A long time ago, when people wanted to build electrical circuits, they needed a nice flat piece of wood to connect everything to.
They often used breadboards since they were a great shape and it was easy to screw components onto it.
Nowadays we build circuits onto smaller plastic boards that have wiring underneath them and holes on top.
We still call these plastic boards BREADBOARDS, it's sort of a throwback term to the original way of making circuits.
They are also called "solderless breadboards" because you don't have to solder anything together to get the circuit to work.
Another term people use for these things is a "protoboard" that's because engineers will build prototypes of circuits on these boards, then they test them out, and if they are working, then they build a real circuit, perhaps as a smaller version of the prototype.
To get an understanding of how the breadboard works, watch this video:
Breadboards have connections underneath the plastic cover that we can't see.
It's important to understand these connections before you begin to build your circuits.
Take a look at the image below, it shows how the different parts of the breadboard are connected...