Most rivers flow in one broad channel of water, but some rivers split into lots of small channels that continually split and join each other to give a braided appearance. These are called braided rivers.
Braided rivers are usually wide but shallow. They typically form on fairly steep slopes and carry large amount of coarse-grained sediments. When the river's flow decreases, these sediments get deposited on the river bed leaving behind small temporary islands of sands that cause the river's channel to split.