Since its recovery in 1982, Comet Halley has been the focus of an unparalleled global scientific effort of exploration. Remote and
in-situ measurements were conducted from the ground, from Earth orbit, from Venus orbit, from interplanetary space, and from the comet itself. Many discoveries, such as the presence of an unexpectedly large and dark nucleus or the abundance of organic presence of organic material, have led to major changes in our ideas about the general nature of comets. In this report, results of various studies are summarized.