In the US short-term capital gains (held less than one year) are taxed at the same rate as regular income (from work, etc.), -which is a higher rate.

Long-term capital gains (held for a year or more ) are taxed at a more favorable rate, with a maximum of 23.8% payable in taxes (for 2021).

Both short-term and long-term capital gains are considered part of your overall income.