What are the differences between IBIS models and Spice models?

Description

A Spice model is a circuit description at the transistor level. It is a physical model as physical elements are being described. It contains detailed information of all the circuit description within a semiconductor device and is therefore regarded as proprietary by semiconductor vendors.

IBIS models represent the input-output (I/O) behavior of a device. IBIS models contain tables of data that catalog how an input or output behaves electrically.