You already used the breadboard but we totally forgot to talk about it. We can use a breadboard (protoboard) to connect electrical components. Inside the breadboard are metal clamps. Since metal conducts electricity, components in the same clamps are connected. In that illustration you can see which holes of a breadboard are connected internally.
Do you see that the resistor sticks with one leg in the same column like the green LED? That is the point where they are connected.
Expert Knowledge: Conductors and Insulators
Why does the metal clamps make a connection, but not the plastic of the breadboard? There are electrical conducting materials. They are called conductors. Metalls, for instance silver, copper or aluminium are very good conductors. They conduct, because they’ve got so called freely moving electrons. This is actually what current consists of.
Materials without the ability of conducting electricity are called insulators. Plastic, ceramic and glas belonging to the group of insulators. Maybe you’ve already seen the large insulators on high-tension power lines? They hold the cables to the high-voltage poles. Usually they are made of ceramic.
In the past, people put nails into small wooden boards to connect electrical components with wired twisted around it. Because the boards looked a bit like breadboards, they were called like that.