A stop loss order is used to buy or sell a security when it reaches a certain price (it can protect a long or a short position). Execution at that price is not guaranteed because the stock can gap up down, resulting in a fill much worse than the stop loss price.
In a long stock collar, for every 100 shares that you own, sell an out-of-the-money (OTM) call and use the proceeds to buy an OTM put. This defines a floor beneath which you cannot lose as well as a ceiling, beyond which you will not profit.
Collars can be structured for no cost. If you want to skew the risk graph so that you have more upside potential than downside risk, the call sold will be further OTM (or the put closer to the money) and the collar will have a net cost. Skewing the collar in the opposite manner (the put is more OTM than the call is OTM) will result in a net credit but potential loss will be greater than the potential profit.
A pending dividend affects option premium. Put premium will inflate and call premium will deflate. Therefore, the larger the dividend, the more expensive a collar becomes.
If you do 1-3 month collars and the stock appreciates toward the short call strike, you may be able to roll the collar up and/or out, protecting some of your capital gain. Wash, rinse, repeat.
Caveat? Don't monkey with collars if you don't want to sell the stock.
Collared long stock is synthetically equal to a vertical spread. That means that they have similar performance and similar risk graphs. For more info Google: “Synthetic Option Positions”