What does vibrato mean in singing?

A vibrato is a natural pulsing effect produced by breath support and pressure. The vibrato normally starts to develop in later teen years and into the early twenties. By the time you're thirty-five or older, the vibrato is very distinct and rich. The vibrato is a sort of "cheat" to help hold your breath support longer, but it cannot be a forced vibrato. The vibrato will be natural, and you will recognize it when you hear it. A forced vibrato will actually harm your breath support and your pitch will suffer. When you engage your breath properly, the vibrato will kick in on its own.