Polls the keyboard (7B86) until a key is pressed, counting the polls down from the value at $B604. Each poll includes the 1000-iteration delay in 7B6B, so it takes something like 8 ms, and the starting value of 3000 set by 6DCD gives the player roughly 20-25 seconds (my estimate from the instruction timings).

When a key is pressed, 500 is added to what is left of the count, up to a maximum of 3000, so steady typing keeps the time topped up.

If the count runs out, the game takes over: whatever has been typed is erased (6E82), the four characters 'WAIT' from 7288 are put into the input buffer and printed, B is set to $7C (four characters used), the count is reset to 3000, and an ENTER is returned as if the player had pressed it. The line editor then finishes the line and the WAIT command is carried out. This is how time passes in The Hobbit even when the player does nothing, and why the other characters can go off and do things - or attack you - while you are thinking.