The micro connector has A and B types, also there is a universal Micro Female Connector to plug with both Micro-A and B Male connectors.
Micro A connector is in square shape while Micro B connector is in the trapezoid.
Because the Micro-A connector is too square and is easy to be plugged wrongly, so it was eliminated.
Micro B connector is still to be used till now, it is also well known as the Android charging port connector.
Before Type C was commonly used, Micro B is widely used for mobile phone charge cable and was called Android charge connector.
Because it's smaller than Mini B, so Mini B was out too.
Every home must have several pieces of Micro B USB cables, but many of you don't have Mini B data cables anymore.
Micro 3.0 Micro-A and Micro B connectors are different from 2.0 version connectors.
For the same square shape reason of Micro USB3.0 A, it was out and only Micro B 3.0 was used and be widely used for some hard disks.