It can be easily said that op amps are present in almost all electrical devices and can be used for various applications, depending on the external components/circuitry or topology.
Differential amplifier (difference amplifier)
Amplifies the difference in voltage between its inputs.
Inverting amplifier
An inverting amplifier is a special case of the differential amplifier producing an output which is 180° out of phase with respect to its input.
Non-inverting amplifier
In this case, the output voltage is always in phase with the input voltage, which is why this topology is known as non-inverting.
Voltage follower (unity buffer amplifier)
This circuit does not generally require external components, and provides high input impedance and low output impedance, which makes it a useful buffer.