Use robust to describe a person or thing that is healthy and strong, or strongly built. This adjective also commonly describes food or drink: a robust wine has a rich, strong flavor.
If your school has a robust sports program, it means they offer lots of different kinds of sports and that a lot of kids participate. If you have a robust speaking voice, it means you have a voice that's deep and loud and strong. Robust is from Latin robustus "of oak, hard, strong," from robur "oak tree, strength."