  The James Webb Space Telescope (JWST) will revolutionize our understanding of
exoplanets with transit spectroscopy of a wide range of mature planets close to
their host stars ($<$2 AU) and with coronagraphic imaging and spectroscopy of
young objects located further out ($>$10 AU). The census of exoplanets has
revealed an enormous variety of planets orbiting stars of all ages and spectral
types. With TESS adding to this census with its all-sky survey of the closest,
brightest stars, the challenge of the coming decade will be to move from
demography to physical characterization. This white paper discusses the wide
variety of exoplanet opportunities enabled by JWST's sensitivity and stability,
its high angular resolution, and its suite of powerful instruments. JWST
observations will advance our understanding of the atmospheres of young to
mature planets and will provide new insights into planet formation.
