  I review the current status of the theory of Cosmic Inflation. My discussion
covers the motivation and implementation of the idea, as well as an analysis of
recent successes and open questions. There is a special discussion of the
physics of ``cosmic coherence'' in the primordial perturbations. The issue of
coherence is at the heart of much of the success inflation theory has achieved
at the hands of the new microwave background data. While much of this review
should be useful to anyone seeking to update their knowledge of inflation
theory, I have also made a point of including basic material directed at
students just starting research.

Astrophysics;General Relativity and Quantum Cosmology;High Energy Physics - Theory