When you kneel, you rest your bent knees on the ground. People kneel to pray, to work in the garden, and to do yoga.
Kids often kneel on the living room rug to play, and adults kneel to tie a child's shoelaces, to vacuum under the sofa, to play with a puppy, to exercise, and for many other reasons. A great thing about the word kneel is that its meaning is easy to see — the word knee is obvious when you look at it. The Old English root word, cnēowlian, simply means kneel, and it comes from cnēow, or "knee."