When shopping for computers or ther gadgetry, you will encounter a lot of short-hand terminology that describes the internal components of the system. This terminology explains the capabilities of the components, such as the amount and type of memory.

Defining MB

MB stands for megabyte. One megabyte can contain about a half million words of text. Mb stands for megabit. There are eight bits in a byte. Sometimes the letters are not capitalized, but "mb" usually means megabyte, informally.

Defining Memory

DDR memory is a type of RAM (Random Access Memory). RAM comes in "sticks" installed on the motherboard inside your computer. These sticks usually go in slots near the CPU (Central Processing Unit). Sticks snap into brackets to hold them securely.

How RAM Works

Your computer uses RAM to rapidly store and retrieve commonly accessed information. RAM is much faster for this than your hard drive, so it will be used constantly. Fortunately, RAM can last for years despite heavy use, since it has no moving parts.

Putting It All Together

"512 mb ddr memory" refers to 512 megabytes of RAM. You can buy sticks containing this amount, or the phrase may be referring to RAM already installed in a computer. 1024 megabytes add up to one gigabyte.

Shopping Decisions

If you are shopping for this RAM, check your computer's motherboard manual to make sure the stick is compatible, and visually inspect the slots on the board to make sure you have empty ones for more memory.

Source:

System memory overview

DDR speed chart