1. EDO RAM (Extended Data Out)
-This comes in capacity of 8MB and 16MB
-It runs at speed of 66 MHz
-It uses SIMM slots.

2. SDRAM (Synchronous Dynamic RAM)
-It comes in capacity of 16MB, 32MB, 64MB, 128MB and 256MB.
-It runs at a speed of 100,133,166 MHz

3. DDR-SDRAM (Double Data Rate) -It comes in 3 types
DDR1 –Capacity of 256MB, 512MB, and 1GB.
Speed of 200, 266, 300, up to 400 MHz

DDR2 –Capacity of 512MB, 1GB, 2GB, 4GB.
Speed of 400 up to 800 MHz

DDR3 –Capacity of 1GB, 2GB, 4GB, 8GB and 16GB.
Speed of 1GHz and higher.

4. VRAM/WRAM (Video RAM/Windows RAM)
-These are used to graphic memory in graphic cards.
-VRAM comes in capacity of 8, 16, 32 MB.
-WRAM comes in capacity of 32, 64, 128 and 256 MB.
-Latest graphic cards now are DDR2/DDR3 technology.