Longtermism is the claim (or thesis) that we can do the most good by focusing on effects going into the longterm future:
Let strong longtermism be the thesis that in a wide class of decision situations, the option that is ex ante best is contained in a fairly small subset of options whose ex ante effects on the very long-run future are best.
Longtermism is the claim (or thesis) that we can do the most good by focusing on effects going into the longterm future:
https://globalprioritiesinstitute.org/hilary-greaves-william-macaskill-the-case-for-strong-longtermism/