The top or beginning of a set of stairs.
The stairhead is where the stairs start or end, and it can make people think of going up or down.
Examples:
The cat is at the stairhead.
I am standing at the stairhead.
The stairhead is where we start to go up.
The mouse is at the stairhead, looking down.
At the stairhead, there is a big, scary monster.
I always stop at the stairhead to catch my breath.