Schedule D is a summary sheet. Individual transactions are listed on form-8949 and totalled into Schedule D by category, with section-1256 results arriving from form-6781 and fund distributions from other statements.
It performs the netting in a set order, applies the $3,000 capital-loss-limitation against ordinary income, and produces the figure carried forward under capital-loss-carryover. The tax computation worksheet behind it applies the preferential rate bands.
Traders with thousands of transactions usually attach broker statements in summary form where the reporting category allows it rather than listing every line, provided the totals reconcile to form-1099-b.
This is general information for the United States, not tax advice. Rules change and depend on your circumstances; consult a qualified professional.
Related: form-8949, form-6781, capital-loss-carryover, capital-loss-limitation, form-1099-b