Operational Amplifier, like any electric or electronic component, can be represented in diagrams by a schematic symbol.
There are more than one schematic symbol and this happens because sometimes it is not necessary to outline all the connections of an Operational Amplifier.
We see the 3 main used symbols.
The first is the simplest:
As you see Operational Amplifier has two input pins and one output pin.
V+ pin is called non-inverting input pin and the V- pin is called inverting input (we'll explain soon the meaning of these names).