This is a 3.3V/5V MB102 Breadboard Power Supply Module which provides a dual 5 V and 3.3 V power rails and has a multi-purpose female USB socket.
The breadboard is the most essential tool for an electronics engineer. It makes prototyping a breeze. One of the first things an electronics engineer/hobbyists need is a breadboard to quickly try out the projects before soldering down on a PCB.