What is the difference between USB flash drives and USB Micro Drives?

The term USB flash drive is a generic phrase used to describe of these products without specifying a particular manufacturer. USB flash drives are sold by many different companies under a variety of different proprietary product names. The term USB flash drive is used in the same manner that the term DVD and CD-RW are used; to describe the technology in generic terms.

It is likely that other names you have heard used to describe these products are actually proprietary product names intended to describe a specific USB flash drive model made by a specific company.