The LM 741 is a single OP-AMP in an 8-pin chip**.
It is the most widely-used op-amp in the world.
It can operate from a single 9v supply or up to +18v/-18v (741C).
As the frequency increases, the maximum gain decreases. Unity gain occurs at 1.5MHz.

See our 3 page article on OP-AMPs in the subscription section: Basic Electronics Course pages 72, 73 and 74.
It shows an animated OP-AMP with varying voltage on the inputs and the voltage on the output.

Circuits using an LM 741: