File that reads commands file?

[ktb <ktb@binary.net>]

Hi, I was wondering does each distribution of Linux have slightly
different commands, in say bash?  I was thinking if they are different,
then the books I am looking at  are off because most of them are based
on Red Hat.  So if that is the case I think it would be a good idea  to
find the files in my personal distribution that execute commands if
there are such things?  Then if  something I read doesn't work I don't
have to always assume it is me and I can look and see if the command is
supported.  Well, I could learn to do so.  If so what are some of the
names?   I am quite new to this so I hope I don't have to look at some
of them in root:)
Kent