RTFM

RTFM is often (rudely) used to mean don't bother me; I'm busy, or it is used as a stronger form of abuse. The strange thing is that asking you to read a manual is most often very good advice. Take the advice! The most important point to remember is that you should refer to a manual whose release version matches that of the server on which you are operating.

The PostgreSQL manual is very well written and comprehensive in its coverage of specific topics. However, one of its main failings is that the documents aren't organized in a way that helps somebody who is trying to learn PostgreSQL. They are organized from the perspective of people checking specific technical points so that they can decide whether their difficulty is a user error. It sometimes answers what? but it seldom answers why? or how?.

I've helped write sections of PostgreSQL documents, so I'm not embarrassed to steer you toward reading them. There are, nonetheless...