If you say that something is okay, you find it satisfactory or acceptable.

If you say that someone is okay, you mean that they are safe and well.

Okay means in a satisfactory or acceptable manner.

You can say 'Okay' to show that you agree to something.

You can say 'Okay?' to check whether the person you are talking to understands what you have said and accepts it.

You can use okay to indicate that you want to start talking about something else or doing something else.

You can use okay to stop someone from arguing with you by showing that you accept the point they are making, though you do not necessarily regard it as very important.

If someone in authority gives something the okay, they officially agree to it or allow it to happen.

If someone in authority okays something, they officially agree to it or allow it to happen.