This question already has an answer here:
For external packages CTAN provides the needed documentation, however, for built-in Latex commands I am not aware of any proper documentation except for The (not so) short introduction to Latex which doesn't really list all the options
I would like to know how I could check all the available environments, commands and relative optional fields of all the built-in commands of Latex more or less like I would use the
man command under linux.
I'm looking for something exhaustive like the KOMA-script documentation that breaks down every single piece available.