Explain the similarities and differences between pigeonholing a bill and exercising a pocket veto.

In the U.S system, the President was ten days to decide what to do with a bill passed by  Congress. If he signs it, it becomes a law. If he vetoes it, it goes back to Congress, which can override the President's decision and still make it a law if two thirds of both houses agree. But if the ten days goes by, the President hasn't make any with the bill and the Congress adjourns before the ten days is up, the bill is vetoed and cannot go back to Congress, so the President can't be overrode.

A pigeonhole is when a bill is put aside for a better time to pass it or to kill it.

which time period is this? or is this story fictional, i'm going to need more info to answer this question