You can wash bedsheets with towels if you want. Lots of lint, sand, and many other unpleasant contaminants will come out of those rugs. Don't use bleach unless you have the funds for a new pair of sneakers. Remove the laces first. For expensive brand-name athletic shoes, follow manufacturer recommendations.
Darks are darkly or boldly colored items.
Lights and darks are washed the same way, without bleach. The idea of separating them is to keep dyes that may bleed from dark clothes off the light clothes. Also, dark lint from dark clothes will show more on light clothes, and vice-versa. Reds you may want to put in a group of their own, as red dye bleeds notoriously. Finally, check items for pulls, runs, rips, missing buttons, open seams, etc.