Your step the wrong way off a curb and sprain your ankle...or is it a strain?
A strain is when you badly stretch or tear a muscle. A sprain is when you stretch or tear ligaments, or part of a ligament.
Ligaments are tough bands of connective tissue, kind of like thick rubber bands, that connect bones to each other. Ligaments are strong, but they can get damaged when you change direction suddenly or land awkwardly on your foot, that sort of thing.