Corporations
The term corporation, for federal income tax purposes, generally includes a legal entity treated as separate from the persons who formed it under federal or state law or the shareholders who own it. It also includes certain businesses that elect to be taxed as a corporation by filing Form 8832, Entity Classification Election. Corporations report their income and expenses, and calculate their tax on Form 1120, U.S. Corporation Income Tax Return. For more information on corporations, refer to Publication 542, Corporations. Corporations that meet certain requirements may elect to be taxed under subchapter S of the tax code by filing Form 2553, Election by a Small Business Corporation. S corporations file Form 1120-S, U.S. Income Tax Return for an S Corporation and are generally not subject to regular income tax. Most income and expenses of an S corporation are passed through to the shareholders on Schedule K-1 (Form 1120-S) and/or Schedule K-3 (Form 1120-S). The shareholders report on their income tax returns the amounts indicated on the Schedule K-1 and/or Schedule K-3. For more information on S corporations, refer to the Instructions for Form 1120-S.
Source: https://www.irs.gov/taxtopics/tc407
A corporation is an entity that is owned by its shareholders (owners). Corporations can be taxed 2 different ways.
C corporation
Generally taxed on their income and the owners are taxed on these earnings when distributed as payments or when the shareholder sells stock
S corporation
Generally taxed on their income and shareholders are taxed on their share of the S corporation’s taxable income whether payments are distributed or not.