An opamp is a circuit of many components. It may either be built of many discrete components or be a single integrated component.

A discrete component is one where the package contains only one circuit element. The opposite is an "integrated circuit" (aka a "silicon chip" or "chip") where a package contains many circuit elements.

It's not that "discrete" is a type of resistor, it's that a resistor is a type of discrete component.

discrete transistors

A discrete device/component is not installed directly on the motherboard. See Discrete Graphics Card.

Resistors, capacitors, diodes any component that is a recognized item byitself as a single component.