What is the electricity and circuit?

When a metal wire is connected across two terminals of a voltage source with positive and negative terminals, the source develops an electric field across the metallic wire. This field forces negative charge or electrons to flow towards the positive terminal. That negative charge is nothing but current or electricity. It is measured in amperes(A).

In simple terms, electricity is the flow of negative charges or electrons.

Mathematically,   

$i = \frac{v}{r}$ where, i = current, v = voltage, r = resistence

A circuit is a path or a way through which electricity flows. It starts at a source, like a battery, and flows through a wire to a bulb or other object and back to the other side of the power source. Indeed an electronic circuit consists of individual electronic components, such as resistors, transistors, capacitors, etc connected by conductive wires through which electric current can flow.