1) Take off( remove) your neckless. 2) Do not use your phone while the plane takes off (leaves) 3) I'm about to take off from work. ( leave work for a period of time)

Mike gave some good examples and usages. It can also mean to suddenly improve, e.g. "His career has really taken off since he moved into IT". It can also be a slang term to mean something like "copy or emulate by acting", e.g. "Did you see his take off of the President? It was hilarious".

The online Collins Dictionary is excellent. It gives nine meanings and many examples. https://www.collinsdictionary.com/dictionary/english/take-off

it's a phrasal verb that means "to remove"