Tights are a form of hoisery similar to pantyhose; they have the same basic design but are much thicker. Most tights are at least 50 denier thick, which allows them to be much more colorful than pantyhose, which are usually only 5-15 denier.
Colored pantyhose serve to change the skin tone color of the legs slightly. Tights are more drastic, in that they are solid (or patterned) colors that are intended to change the color of the legs completely. Tights can also be a nude color so the legs seem to retain their original color, but will cover up any cuts or bruises on the legs which pantyhose won't be able to conceal.
Race Queens are the defacto example of legs with tights on. Granted they are normally nude in color they can also be shiny. Tights can be pulled higher up the waist allowing for more higher cut leotards or other clothing to be worn without seeing the "rings" that most panythose have near the top of the thigh. Tights are preferable to pantyhose in that they are much thichker and won't "run" when snagged on something. Costumes that have any king of semi-sharp or even edged accessories that might constantly rub against the legs, tights are preferable as they won't tear as easily.
