Original: The newer Micro-USB receptacles are designed to allow up to 10,000 cycles of insertion and removal between the receptacle and plug, compared to 500 for the standard USB and Mini-USB receptacle.
Simplified: The newer USB micro receptacles are designed to allow up to 10,000 cycles of insertion and exertion between the receptacle and plug, compared to 500 for the standard USB and Mini-USB receptacle.