Definition of “past” - Learner’s Dictionary

past

noun uk us /pɑːst/
the past

B1 the time before the present and all the things that happened then:

the distant/recent past
In the past people would bathe once a month.

A2 the form of the verb which is used to show what happened in the past

sb's past

B1 all of the things that someone has done in their life:

I knew nothing about his past.

(Definition of “past noun” from the Cambridge Learner's Dictionary © Cambridge University Press)