Why Different Commands ?

[Vilas Sukhadeve]

Dear Friends,
I am used to Ubuntu 5.10 for almost an year and I despise using MS
programmes. I am not any software man rather I am "computer
illiterate".And whenever I faced any problem with operating any
programme, all of you have helped me. This is very nice with, I will
call our community. (I wanted to make our community bold but in
Evolution these icons are not functioning, can anybody tell me how to
activate them ?) 
Here I would like to know why different commands have to be used in
Terminal. e.g. sudo, apt-get, chmod, mkdir, #, I know only these
commands so far. What these different commands stand for ? If you feel
this is just child like query but still as a responsible parent please
tell me just for my information.
Thanks !
With Love and regards
Vilas
(India)