You can just declare that as "self-employment" in your tax return. No need to create a corporation.
But, it is a company. Just with yourself as the only employee. The tax form for that is the Schedule C. Note that depending on the amount of money you get, you should pay taxes every quarter, to avoid penalties on April 15. And you of course can deduct business expenses for things you use in the business.
Because of all this, if you don't know these things, you should go to a CPA to get everything right.