What are two kind of memory in a computer?
That depends on what you mean by "Memory". If you are talking generally then there is Hard Disk Memory, Flash Memory, and RAM (Random Access Memory), usually when referring to memory in a computer though people are talking about the RAM. There are 4 types of RAM (That I know of) which are SD RAM, DDR, DDR2 and DDR3.
First, you need to know what kind of memory your computer uses. Then find out how much memory you already have. You need to review your manual to see what type of memory your computer supports. Then open up the computer to see how many memory slots you have available. Once you find out that information you will be able to buy more memory and install it on your computer.