For young children, I've found that a good way to explain the process is to tell them that each of their toys has a home. Toys that are left on the floor or anywhere they don't belong are lost, and the child needs to help them find their way to their home. If there are any toys that don't have a home, the child should make a home for them.
This little trick is a great way to teach very young kids about cleaning, and to explain the concept of, "a place for everything and everything in its place." It helps them take ownership over their things by giving them control over where they choose to keep them. It also makes clean-up time something of a fun experience as the children pick up each toy and say, "Hello Mr. Teddy! Are you lost? Here, your home is right here on my bed. There you go!" and "Oh, poor little block. You are sitting out on the floor all by yourself. Let's go get you back with the rest of your friends in the block box."
Now if only I could teach my husband to help his dirty socks find their way to their home in the hamper... ;-)