When are wal released or removed in postgresql?

I am relatively new to postgresql administration and I still have doubts about the operation or management of the wal files, specifically how these files are released or deleted, have the conception of Oracle which is what I know the most, where the redologs exist , which do a similar function, saving the differences, but in the case of redologs, the administrator establishes the size, quantity and specific groups, now in postgresql it is not clear to me, wals are generated to record the activity (changes) in the database, if it has a lot of activity of this type, more wal is generated, collapsing the file system, when these wal files are deleted?