Imagine you are playing with some sticky mud and a bucket of water outside on a sunny day. You put some mud into the water and mix it all around. Then you let the water flow away and notice that the muddy water is moving in different directions, almost like it's braiding.
A braided river is a lot like this. It happens when a river carries a lot of sediment (tiny rocks, sand, and mud) and it starts to flow in different directions as it searches for the easiest way to move the sediment. The river creates little channels of water that twist and turn around each other, similar to how you might braid someone's hair.
These channels can be small or large, with islands of sand and rocks forming in between. Sometimes the channels will join together and then split apart again, which creates a really unique and cool-looking river pattern from above.
Braided rivers are found all over the world, but they're most common in dry areas with lots of sediment, like in the mountains or deserts. People can go rafting or kayaking on these kinds of rivers, but they should be careful because the braiding channels can change quickly, and the water can be quite fast and strong.