a) open a console/ terminal and type:
b) read it up : here's all of them commands documented:
EDIT: dang, the lifewire article did not really document most commands, only listed them. Instead go to the source:
You must be registered to see the links
/EDIT
which is not the best solution, as many of them are highly specific and never needed by "normal people"/ for "normal purposes", but for looking up one or two specific commands - fine.
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when I first started with computers myself, I did so with Suse Linux 4.2.
The best thing about it was: it came with a book, documenting most common commands (and bash itself).