Service mark symbol. The service mark symbol (â ), the letters SM in superscript style) is a symbol used in the United States to provide notice that the preceding mark is a service mark.
Size matters: The micro and mini USB connectors are of similar width. But the micro connector is much thinner (smaller vertical dimension). Some product designs were not able to accommodate the height of the mini receptacle and the new thinner receptacle will encourage and allow thinner products.
The A end goes into the host (usually the computer) and the B end into the peripheral (your Nexus). The standard B end is the chunky one, mini is the one halfway in between, and the current micro ones are the tiniest. They are all B ends of the cable.