SIMD stands for Single Instruction, Multiple Data. It is a way for the CPU to speed up operations when dealing with data that requires being processed by the same instruction. Let's assume you have 10 pieces of data; you'd normally need to execute the same instruction separately for each data chunk, with each piece of data and each instruction taking up one CPU cycle. Using SSE, you can skip 9 of those wasted instructions, and instead tell the CPU to execute the next ten items of data using the same instruction, which save CPU time for other operations.