Soon I will be coming into a bit of extra money. Rather than simply sticking it in a savings account I would like to make my money work for me and getting into stock seems to be a good way to do that.
This is a very good question!
The biggest difference is that when you put money in a savings bank you are a lender that is protected by the government, and when you buy stocks you become an owner.
As a lender, whether the bank makes or loses money on the loans it makes, they still maintain your balance and pay you interest, and your principal balance is guaranteed by the government (in the USA). The bank is the party that is primarily at risk if their business does not perform well.
As an owner, you participate fully in the company's gains and losses, but you also put your money at risk, since if the company loses money, you do too. Because of this, many people prefer to buy funds made up of many stocks, so they are not at risk of one company performing very poorly or going bankrupt. When you buy stock you become a part owner and share in the profitability of the company, often through a dividend.
You should also be aware that stocks often have years where they do very poorly as well as years when they do very well. However, over a long period of time (10 years or more), they have historically done better in outpacing inflation than any other type of investment. For this reason, I would recommend that you only invest in the stock market if you expect to be able to leave the money there for 10 years or more, ideally, and for 5 years at the very least. Otherwise, you may need to take the money out at a bad time.
I would also recommend that you only invest in stocks if you already have an emergency fund, and don't have consumer debt. There isn't much point in putting your money at risk to get a return if you can get a risk-free return by paying off debt, or if you would have to pull your money back out if your car broke down or you lost your job.
If you have money and may need to access it at any time, you should put it in a savings account. It won't return much interest, but it will return some and it is easily accessible.
If you have all your emergency savings that you need (at least six months of income), buy index-based mutual funds. These should invest in a broad range of securities including both stocks and bonds (three dollars in stocks for every dollar in bonds) so as to be robust in the face of market shifts.
You should not buy individual stocks unless you have enough money to buy a lot of them in different industries. Thirty different stocks is a minimum for a diversified portfolio, and you really should be looking at more like a hundred. There's also considerable research effort required to verify that the stocks are good buys. For most people, this is too much work. For most people, broad-based index funds are better purchases. You don't have as much upside, but you also are much less likely to find yourself holding worthless paper.
If you do buy stocks, look for ones where you know something about them. For example, if you've been to a restaurant chain with a recent IPO that really wowed you with their food and service, consider investing. But do your research, so that you don't get caught buying after everyone else has already overbid the price. The time to buy is right before everyone else notices how great they are, not after.
Some people benefit from joining investment clubs with others with similar incomes and goals. That way you can share some of the research duties. Also, you can get other opinions before buying, which can restrain risky impulse buys.
Just to reiterate, I would recommend sticking to mutual funds and saving accounts for most investors. Only make the move into individual stocks if you're willing to be serious about it. There's considerable work involved. And don't forget diversification. You want to have stocks that benefit regardless of what the overall economy does. Some stocks should benefit from lower oil prices while others benefit from higher prices. You want to have both types so as not to be caught flat-footed when prices move.
There are much more experienced people trying to guess market directions. If your strategy relies on outperforming them, it has a high chance of failure. Index-based mutual funds allow you to share the diversification burden with others. Since the market almost always goes up in the long term, a fund that mimics the market is much safer than any individual security can be. Maintaining a three to one balance in stocks to bonds also helps as they tend to move in opposite directions. I.e. stocks tend to be good when bonds are weak and vice versa.
Generally, a share of stock entitles the owner to all future per-share dividends paid by the company, plus a fraction of the company's assets net value in the event of liquidation. If one knew in advance the time and value of all such payouts, the value of the stock should equal the present cash value of that payout stream, which would in turn be the sum of the cash values of all the individual payouts.
As time goes by, the present cash value of each upcoming payout will increase until such time as it is actually paid, whereupon it will cease to contribute to the stock's value.
Because people are not clairvoyant, they generally don't know exactly what future payouts a stock is going to make. A sane price for a stock, however, may be assigned by estimating the present cash value of its future payments. If unfolding events would cause a reasonable person to revise estimates of future payments upward, the price of the stock should increase. If events cause estimates to be revised downward, the price should fall.
In a sane marketplace, if the price of a stock is below people's estimates of its payouts' current cash value, people should buy the stock and push the price upward. If it is above people's estimates, they should sell the stock and push the price downward. Note that in a sane marketplace, rising prices are a red-flag indicator for people to stop buying. Unfortunately, sometimes bulls see a red flag as a signal to charge ahead. When that happens, prices may soar through the roof, but it's important to note that the value of the stock will still be the present cash value of its future payouts. If that value is $10/share, someone who buys a share for $50 basically gives the seller $40 that he was not entitled to, and which the buyer will never get back. The buyer might manage to convince someone else to pay him $60 for the share, but that simply means the new buyer is giving the the previous one $50 that he wasn't entitled to either. If the price falls back to $10, calling that fall a "market correction" wouldn't be a euphemism, but rather state a fact: the share was worth $10 before people sold it for crazy prices, and still worth $10 afterward. It was the market price that was in error.
The important thing to focus on as a sane investor is what the stock is actually going to pay out in relation to what you put in. It's not necessary to look only at present price/earnings ratios, since some stocks may pay little or nothing today but pay handsomely next year. What's important, however, is that there be a reasonable likelihood that in the foreseeable future the stock will pay dividends sufficient to justify its cost.