Phase locking is when two things start moving together at the same time. It's like when you're playing with your friend and you both start clapping your hands at the same time. You're phase locked! In the same way, phase locking happens in science when two things like sound waves or electricity waves start moving together at the same time.
Imagine you have two pendulums hanging from a wall. You pull one of them back and let it go. It starts swinging back and forth, like a tick and a tock. Now imagine you do the same thing with the other pendulum, but you start it moving at exactly the same time as the first one. What happens? They start moving together, phase locked! They move in perfect harmony, swinging back and forth at the same time.
Scientists use this same idea of phase locking in things like music, where different instruments play different notes but are still in time with each other, and in communication networks when computers or phones send messages at the same time. It's all about keeping things moving together, like a big group of friends doing the same dance at the same time!