How do by-elections happen, and what if Labour loses its majority?

[Wouldcou]

Outside of the general election. Is it because there are MPs that have stepped down?Also what happens if labour loses the majority?

Yes, if an MP resigns or dies, there is a by-election.

Labour has a substantial majority at the moment, so by-elections would not affect it.

. Don't know why I answered a question you didn't ask, sorry.