The MMX instruction set includes 57 new instructions specifically designed to speed up the processing of video, audio, and graphical data. MMX instructions use a Single Instruction Multiple Data (SIMD) that allows one instruction to perform the same function on multiple pieces of data. This reduces the chip's computational-intensive loops that are common with video, audio, graphics, and animation. An analogy for this a classroom teacher to tell the whole class do do the work, rather than telling each individual student one at a time.
MMX technology is standard on Pentium MMX and Pentium II processors. Programs cannot make use of the MMX technology, unless they are specifically written for them.