C corporations file Form 1120.
See https://www.irs.gov/instructions/i1120#en_US_2022_publink11455td0e333
S corporations file Form 1120-S and there are a number of differences between an S corporation and a C corporation. However, the primary difference is that an S corporation is a pass-through entity where all of the income, loss, et al, is passed directly through to the shareholder (you) on a Schedule K-1.
S corporations do not pay federal income tax as do C corporations, but S corporations are considered separate entities, unlike sole proprietorships and single-member LLCs.
See https://www.irs.gov/instructions/i1120s#en_US_2021_publink11515kd0e283
