This is the 122nd most frequent Dutch word.
zitten
"Zitten" means "to sit" or "to be seated."
Here, 'zitten' is used in its primary meaning to express sitting down.
Ik zit op een stoel.
I am sitting on a chair.
In this case, 'zitten' metaphorically indicates the location or source of the problem.
Daar zit het probleem.
That's where the problem lies.
Here, 'zitten' combines with an adverbial phrase to denote a habitual position or state.