What does using right/left/up/down key and option/command key together mean? Using right/left/up/down keys with Fn key can do the same as page down / page up / home / end on a PC.

Some mentioned about using right/left/up/down keys with either option or command key in http://www.apple.com/shop/question/answers/mac/how-can-i-make-the-home-and-end-keys-on-the-apple-extended-keyboard-work-as-line-commands-rather-than-page-commands/Q7HY7K2UFDTUK7J7C .
What do they mean under OS X?

Thanks.
⌘+← or → jumps to the left/right end of the current line
⌘+↑ or ↓ jumps to the top/bottom of the current page
⌥+← or → jumps to the left/right adjacent word
⌥+↑ or ↓ jumps to the start/end of the paragraph
(all terms are respective)