LTspice supplies many device models to include discrete like transistors and MOSFET models. Nevertheless, there are also many third-party models from manufacturers that are available that you could add to your LTspice IV circuit simulations. These third-party SPICE models are described with a .MODEL and .SUBCKT statements. Models given as .MODEL statements are for intrinsic SPICE devices like diodes and transistors. Whereas models given by .SUBCKT statements define the component by a collection of circuitry of intrinsic SPICE devices. This video provides an overview of how to add a third-party .MODEL statement for an intrinsic SPICE device and how to add and create a symbol for a third party .SUBCKT statement to LTspice IV.