Because short-term gains stack on top of wages at marginal rates, a profitable trading year can push you into a higher bracket and into surtax territory. There is no preferential rate and no indexation for inflation.
Short-term losses offset short-term gains first, which is favourable, since they are shielding income taxed at the highest rate. Excess losses then offset long-term gains and finally ordinary income up to the annual limit described under capital-loss-carryover.
Futures and broad-based index options escape this treatment through section-1256 and its sixty-forty-tax-treatment, which is a genuine structural advantage for high-turnover strategies.
This is general information for the United States, not tax advice; rules change and depend on your circumstances, so consult a professional.
Related: long-term-capital-gain, capital-loss-carryover, sixty-forty-tax-treatment, trader-tax-status, schedule-d