A crossbow bolt is a type of arrow that you use with a crossbow. A crossbow is like a big fancy bow that you hold with your hands, and instead of pulling the string back with your hands, you use a special mechanism to do it for you.
The crossbow bolt is basically a long stick with a sharp point at one end, and feathers on the other end that help it fly straight. You put the sharp end into the slot on the crossbow, and then pull the string back so that it holds the bolt in place.
When you're ready to shoot, you aim the crossbow at your target and then let go of the string. The string snaps forward and pushes the bolt out of the crossbow really fast, like a rocket! The sharp point at the end of the bolt is supposed to pierce your target, like a balloon or a target board.
Crossbow bolts are fun to shoot because they're really fast and powerful, but sometimes they can be dangerous too, so it's important to be very careful and follow all the safety rules when using one.