A device for connecting electronic components together when prototyping. Useful because it simplifies electrical connections and eliminates soldering and wire-wrapping.
Diagram
This is what the breadboard in your kit looks like. Sometimes they are bigger, sometimes they are smaller.
Internal
This is the inside of a breadboard. Notice that all the columns are connected but not the rows!
How to wire components
With a broadboard, components can only be connected across the columns and now the rows. Compnents can also be connected across the sides of the board.
Additional Resources
: Pimoroni.com - Anatomy of a Mini Breadboard
: wiring.org.co - What is a breadboard?