Gain on the sale of stock that is not held in a retirement plan or Individual Retirement Account is capital gain reported on Form 1040 Schedule D and then transferred to line 13 of Form 1040, U.S. Individual Income Tax Return.
Capital gains and losses are classified as long-term or short term. If you hold the asset for more than one year, your capital gain or loss is long-term. Short term capital gain is taxed at the same rate as ordinary income; but long-term gains are taxed at 15% (and in some cases less) regardless of your tax rate on ordinary income. See Reporting Capital Gains for more details and links to publications.
I hope this helps for understanding reporting and rates on capital gains.