Okay kiddo, so you know how when you play in the sandbox, little grains of sand move around and sometimes make little piles or bumps? Well, imagine if that sandbox was really big and the grains of sand were bigger too - like the size of small rocks or pebbles.
Now, when water flows in a river or a stream, it can pick up these bigger rocks and pebbles and carry them along with it. These rocks and pebbles are what we call "bedload," because they're kind of like the "bed" that the water is carrying along with it.
Sometimes, when the water is really strong or fast, it can even pick up even bigger rocks and boulders and move them around too!
So basically, bedload is just the bigger rocks and pebbles that get carried along with water in a river or stream.