A series circuit connects components one after another in a single path. Because there is only one path, the same current flows through each component.
What happens in a series circuit
If one component or connection opens, the whole path is broken and current stops. Voltage divides across the components depending on their resistance or behavior.
Series versus parallel
A parallel circuit gives current more than one path. Series circuits are useful for simple chains, current sensing, voltage division, and some LED arrangements.
The easiest way to picture a series circuit is one road with every component on the same road.