1GB DDR vs. 2GB DDR?

DDR stands for Double Data Rate (or some prefer Dual Data Rate) and if you're going to be using Microsoft Vista then 2GB is much better than 1GB (although 1GB will be enough for the computer to function)... if you're using XP or any other Operating System then 1GB is enough

DDR is the type of RAM it is. There is SDRAM, DDR, DDR2, and now they have DDR3 coming out. DDR2 is faster than DDR, and DDR3 is faster than DDR2. You will need to make certain what type of memory your computer uses before you buy a specific type of memory. 1gb should be plenty if you are running XP, but if you play games, or run Vista, you may want 2gb. Vista is harder on resources, so you need a bit more.

Technically DDR (double data rate) is the way a computer bus operates on double data rate (i.e. both on the rise and fall of a clock signal) which means that the clock signal should be twice as fast as the data signal.

If you are talking about DDR SDRAM, simply its SDRAM using DDR technology.

If you are a home user a 1G DDR2 SDRAM would be good enough.

internal RAM memory.

1Gb is enough, 2 G is twice better...(very good for the moment).