zitten

In a sentence

• Ik zit op een stoel.

  I am sitting on a chair.

  Here, 'zitten' is used in its primary meaning to express sitting down.

• Daar zit het probleem.

  That's where the problem lies.

  In this case, 'zitten' metaphorically indicates the location or source of the problem.

• Zit je vaak achter de computer?

  Do you often sit behind the computer?

  Here, 'zitten' combines with an adverbial phrase to denote a habitual position or state.