First of all, Google is your friend. That being said, let's break this down.
What is each mainly used for?
They are both used as the main battle rifle for infantry forces in several countries.
The M16/M4/AR-15 is 5.56/.223, but it is available in just about any caliber you would like from .22 to single shot .50BMG.
The AK47/AKM/AK74 is 7.62x39, but is also available in 5.45x39 and 5.56/.223
What are the price range on these?
Currently civilian models of the M16 (AR-15) can be had for anywhere between $800 and $2500 for standard models, depending on brand and features. There are cheaper and more expensive, but the majority will fall between these price ranges. As for the actual M16, the sky is the limit. You're probably looking somewhere between $15000 and $20000.
The civilian variations of the AK47 can be had for anywhere from $400-1500 depending on model and brand. Again, there are exceptions to the rule, but these are the average prices. A real AK47 is going to run you a lot more, but I assume you are talking about the civilian models that are semi-automatic only.
Do certain manufacturers make each?
Yes, there are countless manufacturers of each.
When ppl think there may soon be restriction on guns these 2 gain popularity at local gun shops here,why is that?
People want to own them, and if it looks like they won't be sold in the future, they want to own them before that is the case. It is argued as hysteria and as preparation. Many people believe that the next president will ban them, and that unless you already own one, you will never be able to get them again. That is why they are flying off of the shelves and the prices have gone up 10-100% depending on location. There are also many people who believe that the ban will not happen or that it will not happen in the near future. The people in this camp beleive that by spring or summer of next year, there will be a surplus of so-called assault rifles, and that the prices will have dropped significantly. Obviously, neither group has been proven right or wrong, so you can make your best judgement as to whether it is worth investing in a rifle now.
Don't mention it.