Usually when we say aqui it means like right here right in front of me and aca is here but a little further away. Same goes for alli alla, alli is there so is alla but alla tends to be a little furtheraway.
Also depending on the country one is usually used more often then the other.
These are interesting grammar concepts and indeed there is a difference between aqu?/ac? vs all?/ all?. I am not interested in debating grammar rules that govern and explain the usage of concepts in Spanish that have been created centuries ago by philologists and grammarians etc. because they are not debatable. I say this in light of a recent thread that is now history.
Most grammar textbooks provide the general meaning of these words but do not go into details which is sometimes necessary for clarity of usage. I had a great professor who used to correct us even when we were speaking if we used these words incorrectly. As well there are great resources that do focus on specific concepts such as these in Spanish.
If you don't get the answers you are looking for I will send you a PM. However, Mofi's post is absolutely correct in terms of the basic differences between each pair of words.
Here's one that might be useful.
Who can explain the differences between aqui and aca, and alli and alla?
I know I missed the accents - I'm lucky to have a computer.
What are the different pronunciations (sp?) of the diffrent accents? When there's an accent on an "a" and "i".....do you just stress that certain letter. I'm going to be starting my spanish classes soon...but in the mean time I've been "self teaching"....so I figure the more I learn going in...the easier it will be to learn
While you are learning, you can be sure you are saying it correctly if you put the emphasis on the accented syllable.
The second to last syllable is often the one with the emphasis, so the accents help a lot when the pronunciation doesn't follow the rule.
Buena suerte. (second to last)