Student or Learner
This is from Collins dictionary.
When people such as the police detain someone, they keep them in a place under their control.
And I searched the word "detain" in google image.
But the images I found were only police taking people somewhere not "keep them in a place".
If you are detained, you could be in a cell, or simply in a room. You could even be detained in the middle of a parking lot. The point is that you are being ordered by the police to stay where you are, or where they tell you to be. You are not "free to go."