An electrical circuit is an assembly of electrical components related to each other by conducting wires.
For a circular current in this circuit, one of the two poles must be a source (a generator) and the circuit must be closed.
The switch is the component that allows the controller to open and close the circuit.
For this simple circuit containing only one source, the usual convention represents the electrical current leaving from the "+" terminal and returning from the "-" terminal. The electrons, whose charge is negative, travel through the circuit in the opposite direction.