Acquaintances are kind of a more superficial relationship. You might meet up every once in a while to hang out or go to lunch but you would not think to turn to them with real, or serious issues that are going on in your life. True friends are there for you for anything, whenever. They are the ones who you can trust while colleagues are individuals you sometimes hang out with or perhaps work with, or even merely individuals you know through other people.
The most important part is that the distinction between aquaintances and real friends is that aquaintances will be there for you regardless of if you're down in the dumps. And they will be there to remain next to you through everything through various challenges and guide you for whatever you need.