I have a Roth IRA and so far I've only contributed to a target fund. If I contribute $500 dollars to the IRA, could I buy whatever I want, such as $500 dollars in Apple stock? If so, when I want to withdraw funds from the IRA, will it be simple to sell the different assets and turn them into cash? I'm not completely sure how this works.
Sure, you can buy individual stocks and other securities* in a Roth IRA, and you can withdraw contributions without tax or penalty (it's only when you have withdrawn all of your contributions and start withdrawing earnings that things get more complicated).
But, it doesn't make sense to "contribute" $500 to buy stock only to pull it back out after selling something else. You might as well just sell $500 of your target fund and use it to buy stock within the IRA. Less paperwork come tax time...
*I'd stop short of saying you can buy "whatever you want" as there are restrictions with non-financial things like real estate, but I don't think that's what you're talking about