A matchlock is a type of gun from a loooong time ago, like hundreds of years ago! Instead of using electricity or batteries to make it work, it used something called a "match" to light a fuse that would shoot the gun.
The match was kind of like a tiny stick that was lit on fire and then used to start a bigger fire, kind of like a match you might use to light a candle, but bigger and stronger. When the trigger was pulled, the lit match would touch the gunpowder and make a big explosion, sending a bullet flying out of the gun!
Matchlocks were very important in battles and hunting back then, because they were able to shoot farther than other weapons, like bows and arrows. But they were also very heavy and hard to carry around, so people had to be very strong to use them. Nowadays, we have much easier ways to shoot guns, like with electricity and batteries, so matchlocks aren't used anymore. But they played a big role in history!