Behest is a noun. It means a request or an order from someone — often someone with power, or someone you feel you must listen to. You almost never meet the word standing alone. People say at the behest of: The changes were made at the behest of the board means the board asked for them, and that is why they happened. It is a formal, slightly old-fashioned word. You will see it in news and in serious writing, not in a chat with a friend. Though actually, it does not tell you whether the ask was gentle or sharp — a behest can be a polite request or a real command. The point is only this: someone wanted it, and that is the reason it was done. There is a very old verb to behest, but almost nobody uses it now.