Android assassins birthed by misguided minds to eradicate the mutant menace, the Sentinels most often have met defeat at the hands of their intended targets: the X-Men, genetic crusaders fighting for peaceful coexistence between the two species of man. The destruction of these mechanical marvels invariably leads to the development of enhanced models, as scientists co-opt various technologies and assimilate past advancements. Now able to alter their forms to keep pace with mutant adaptation, the Sentinels stand poised to descend on an unsuspecting populace!Created by noted anthropologist Bolivar Trask, the first Sentinels were enormous robots designed to track and capture mutants, whom Trask saw as an emerging threat to humanity. Guided by humans or their own artificial intelligence, Sentinels are tireless embodiments of mankind’s hatred and fear of change, a constant threat to every mutant the world over. Ultimately, Trask realized he was mistaken about the threat posed by mutantkind and gave his life to destroy his creations.
The U.S. government later revived the Sentinel program, and secretly controls the bulk of Sentinel research and activity to this day. Most often, the androids have targeted the X-Men. Unwittingly, Mystique's attempted assassination of anti-mutant Senator Robert Kelly precipitated an alternate future in which the Sentinels were allowed free reign to eradicate that mutant menace. They succeeded only too well -- wiping out not only most of the X-Men, but also every other superhuman being they deemed a threat to humanity.
Like their targets, the Sentinels began to evolve as a function of their programming and are no longer limited to humanoid form. Recent advances in Sentinel technology have yielded mutant-Sentinel hybrids and microscopic nano-Sentinels. Countless sanctioned and covert Sentinel bases exist around the globe, operated by both mutant-hunting humans and Sentinels themselves. Each Sentinel enclave may have a slightly different mission, but the androids' primary directive remains the destruction of mutants as a species -- as evidenced by their methodical extermination of Magneto and the 16 million citizens of his mutant haven Genosha.
This is where I got the info. You can search all the characters. Most of them 😛
http://www.marvel.com/bios/bios.htm?id=82&family=X-MEN
Here's a pic.