Few questions about 'how bot works'

Hello,
After 3 years break from programming in c++ I decided to come back and try my luck in doing some stuff with games, as I was always admiring guys doing what they want with any game they want. Actually I have no previous experience with games hacking and asm, but im doing some progress.

Having some knowledge with c++ and basics of asm (still doing lenas tuts) I'd like to ask, how is movement created by bots. I mean, how does bot make character to move? By sending packets or what? Lets say, I found my chars position pointer + offset, is there a way to move my char with it? At first I fought 'change the value and char will move' but it aint that easy.

Just explain, no codes, I want to find it out myself.

Also, can anyone tell me how to unpack .bak file? I tried google and didnt give me an answer. Tried tu make it rar and open, still no effect. If needed I can include the file there ;)

(P.S. Its unprotected game)
Woozi