VRAM or Video RAM is just a type of modified memory that has a fast access speed for use with two way data transfer. This basically means it reads and writes at the same time. Apart from that, you might find it hard to slot a normal chip into a VRAM slot. You'll also find that whatever you fitted it into will not work until you use the VRAM intended, that's just the way it is. That's why the 'P' stands for Parameters.
PRAM is just a small type of memory chip connected to a battery.
I don't have the money for a RAM upgrade. Hey don't panic, there are still a few options to keep your Mac moving along until you get some 'real' RAM chips. If you have a decent sized hard drive, go to the Memory Control Panel in your System Folder and give your Mac a Virtual Memory boost. Set it to 16 or 32Mb and that will help for a while. Virtual is good for a temporary solution, but as with most things for free, you have to pay a price.