Okay kiddo, a loch is a really big lake that can be found in Scotland. It's like a giant puddle of water that's so big, it looks like an ocean.
Now, imagine you have a bathtub at home. You fill it up with water and you can see the water level rising higher and higher. This is because the water has nowhere else to go but up.
In Scotland, the land is shaped like a big bowl, so when it rains or snows, the water gathers in the middle of the bowl and creates a loch. The loch can be so big that it takes up a lot of space and you can sail a big boat on it!
Lochs are really cool because they have their own unique creatures that live in them, like the Loch Ness Monster, which is a big mystery! Plus, people can fish, swim, and do all kinds of fun things around the loch.