Kid Flash is the name of multiple characters in the DC Universe.
The first being Wally West when he was young as an adult replaced Barry Allen in the Flash identity, then Bart Allen became the new Kid Flash.
In other Media
Wally appears in the cartoons: The Superman / Aquaman Hour of Adventure, Teen Titans, Teen Titans Go, New 52's Wally in the Flash series, and the two characters who use the name Kid Flash in Young Justice.