An asian teenager wearing a white shirt with black stripes is sitting on the steps with his face resting on his hand.
The teenager is seated.
"seated " is another form of saying " sitting on the steps."
Sitting is the same as is seated.
Being seated is less technical but is the same action as sitting on the steps. The Asian teenager is the same teenager but there is less detail. The teenager is seated has far less details and does not let the reader picture what is happening in their mind.