Resistors are passive circuit elements i. e they cannot amplify an electrical signal. Obviously from the name, they offer opposition to the flow of current be it in an AC or DC circuit. I remember having to question the use of resistors in an electronic circuit while in secondary school. My teacher fail to explain it to us.


But what is their importance in a circuit? It is to control the flow of current to other components and in a way acting as "current regulator".
Despite being one of the cheapest electronic component, it cannot be overlooked as less important in a circuit.