What's a "turf toe?" I heard the sports guys on ESPN saying one of the NFL players has this problem.

Turf toe is a sprain at the base of the big toe where it meets the foot. The toe gets jammed when running or jumping. Turf toe is ranked third as the injury most likely to cause an athlete to lose time on the field. It's most common in football, soccer, running, and basketball.

The name "turf toe" comes from the fact that many of the players affected by this problem play on artificial turf. Artificial turf is a hard surface. Pushing off, running, and jumping combined together with the hard surface can lead to this injury.