There are two rules we can use to help analyze circuits.

Kirchoff's Junction Rule: The total current flowing into a junction equals the total current flowing away from the junction.

A junction is a place where three or more current paths come together. A branch is a current path that goes between junctions. There is a different current in each branch.

Current is the rate of flow of charge, so the junction rule is really a statement of the conservation of charge.

Kirchoff's Loop Rule: The sum of all the potential differences around a closed loop equals zero.

S DV = 0 for a complete loop.

This is basically a statement of conservation of energy. A charge making a complete loop around a circuit experiences changes in its potential energy as it moves around the loop, but the net change in potential energy for a complete loop is zero.