A sound bite is a small snippet of someone talking. Sound bites are played on the TV and radio.
Just like a bite is a smaller piece of food, a sound bite is a tiny chunk of someone talking: usually an edited part of a longer speech or interview. Journalists are always looking for sound bites — which might be just a few seconds long — that can fit into news shows. Sometimes when a politician says something dumb, it becomes a sound bite that gets played over and over again. Something that's well-said could become a sound bite too.