I started a business last year. How do I know if it is considered self-employed with just a schedule c or some other form?

[KarenL2]

If you are a sole proprietor or single member LLC, you can file as self-employed on Schedule C (unless you elected to be taxed as an S-Corporation - then it's a Form 1120S). 

If you are a Partnership or a multi-member LLC, you will generally file a Form 1065 Partnership return.  If have an LLC and only you and your spouse are members, you will file a Form 1065 Partnership return unless you live in a community property state (then you can file two Schedule Cs).