A clave is a pattern of beats that is often used in Latin music like salsa, merengue, and bossa nova. It's like a special recipe for how to hit a drum or shake a tambourine. The clave pattern is made up of two different kinds of beats - a long beat and a short beat.
The long beat is like the word "strawberry". Say it out loud and you'll notice that your voice stays on the "straw" for a bit longer before quickly moving on to "berry". That longer beat is like the long beat in the clave pattern.
The short beat is like the word "apple". Say it out loud and you'll notice that both syllables take about the same amount of time to say - it's like a quick, sharp sound. That quick sound is like the short beat in the clave pattern.
Together, the long beat and the short beat form a pattern that repeats over and over again. It's like a special dance that the musicians and dancers all follow together. When you listen to music with a clave rhythm, you can try to follow along by clapping your hands or tapping your feet to the beat - just remember that there's a special recipe for this rhythm, with a long beat and a short beat that repeat in a pattern.