  This non-technical review article is aimed at readers with some physics
background, including beginning research students. It provides a panoramic view
of the main theoretical developments in high energy physics since its inception
more than half a century ago, a period in which experiments have spanned an
enormous range of energies, theories have been developed leading up to the
Standard Model, and proposals -- including the radical paradigm of String
Theory -- have been made to go beyond the Standard Model. The list of
references provided here is not intended to properly credit all original work
but rather to supply the reader with a few pointers to the literature,
specifically highlighting work done by Indian authors.
