The battery has two linked jobs in the circuit
The battery provides a
push that keeps the charged particles in motion:
The battery is a store of energy that is emptied more or less rapidly as other stores are filled (by the action of other components in the circuit).
In a complete loop, the battery does both jobs: in a broken loop, neither.
Strictly speaking, the term
battery refers to a number of individual
cells connected in series, and so we might talk about a 1.5 volt cell and a 9 volt battery (which consists of six 1.5 volt cells).
In practice this distinction between battery and cell adds nothing essential to the understandings of the workings of electric circuits. Since the word battery tends to be more commonly used, we'll refer to batteries throughout this topic.
Note that here we've only said what the battery does, not how these two things happen, or how they are linked. As we do that, then we'll be developing a model of an electric circuit.