What do "bank off" and "backboard" mean?
Context:
"A basketball shot made with one hand from a position under or beside the basket (and usually banked off the backboard)"

Question

What do "bank off" and "backboard" mean?
Context:
"A basketball shot made with one hand from a position under or beside the basket (and usually banked off the backboard)"

Answer

The backboard is the board attached to the rim of a basketball goal.  Although called a 'board', it is often made of glass.
To bank the ball off the backboard means to bounce it off the backboard and into the rim.