Collision Theory

Hello everyone,
i already post a similar problem in newbie and debugging section, but that one was a real trouble that make make game unplayable.
this time i want to ask a simple question,
making something like this:
“if they collide, then do what ever you want”
is that all i need to have a “correct collision system” in my game ?
am talking here about bugs similar to this one

http://s20.postimg.org/hn4jc2q49/image.png

in that image the white rectangle stopped moving to the right cause “he” is supposing that “he” already hit the wall.
in the old post about this subject, member “thebebinator” said this :

which i found it correct theoretically but i never tried it.
anyway,
i hope i wasn’t saying nonsense crap :stuck_out_tongue: but am really sure that am not the only one who faced this problem ::slight_smile:

thank you very much