PCB stands for printed circuit board
The PCB is used for mechanical support of the components (e.g. resistor, capacitor, transistor, etc.). .
Let’s say you want to create a water indicator in your home. Here is the circuit for water level indicator
So if you want to make this circuit you need a board that is printed circuit board or PCB . This is the picture of PCB of water level indicator
This for permanent support . If you want to make a prototype then you need a bread board shown below
Image source: Google