What does frequency does in ram

In a short answer yes it increases the speed the processor can process information. The higher the frequency the faster the ram is.

DDR 266 (PC2100) runs at 266mhz and PC2100 is the bandwidth so it will run at 2100MB a second

DDR3 2400 (PC3 19200) can run up to 2400mhz with a bandwidth of 19200MB a second