Maria Hill is a trained SHIELD agent, proficient in interrogation, unarmed combat, marksmanship and the handling and processing of massive amounts of information. She is skilled at directing several operations and operatives at once.
When Maria Hill was older, she joined S.H.I.E.L.D. and eventually rose to the position of commander. After the scandalous affairs of the "Secret War" and its disastrous affect on New York City, Colonel Nicholas Fury went into hiding. Due to Fury's absence, Maria was chosen to be director of S.H.I.E.L.D. by the President himself after he commended her on her work while she was stationed on assignment in Madripoor. Although many others, who she herself admitted were better suited for the position, were not considered for directorship she was assigned as director. Later, it was revealed that Maria was chosen over the other candidates because they were considered "Fury Loyalists" and the President felt that S.H.I.E.L.D. needed "new direction." (To learn about the above highlighted team, character, and/or place, just click on their names. Note: Beware of some in revealing outfits in the background of Nick Fury's bio page.)
At first, Hill had her differences with Iron Man (Tony Stark) and the New Avengers. Mainly due to the fact they withheld information on the "House of M" event leading to "M-Day." After Hill arrested Spider-Man, unmasked him, and used S.H.I.E.L.D. psychic agents to probe his mind for information regarding the "House of M" events, Maria redeemed herself to the Avengers by ignoring the President's order to nuke the island of Genosha. She had made the decision to refuse the President's orders because the Avengers were still on the island at that time. (Click on the highlighted names above to learn about the characters, team, event, and/or place. Note: Beware of revealing outfits worn by some on the House of M's bio page.)
Before the Superhuman Registration Act was passed as law, Hill met with Captain America (Steve Rogers) aboard the Helicarrier and proposed that he lead the Avengers within the law and arrest anyone who would not comply. However, Captain America declined her offer, stating that he would not arrest people who risk their lives for their country every day of the week. Upon Cap's failure to comply, Hill ordered her superhuman response team (aka Cape Killers) to tranquilize Captain America. During the scuffle though, Captain America avoided being tranquilized and escaped becoming the de facto leader of the Secret Avengers. (To learn about the above highlighted act, character, vehicle, and/or teams, just click on their names.)
At one point, S.H.I.E.L.D was dissolved and replaced by H.A.M.M.E.R. When this happened, Maria Hill was fired by H.A.M.M.E.R.'s leader Norman Osborn because he knew that Maria was still secretly working with Tony Stark. After being fired, Maria began to work even more closely with Tony and helped him on various missions. Hill and Stark grow closer in their time spent together, even having romantic encounters on occasion. (To learn about the team and/or character above, just click on their highlighted names.)
Later on, after Osborn invades Asgard during the events of Siege, Maria arrives before the Avengers on her own with a huge gun. In fact, when Thor was beaten down by Osborn and his "Dark Avengers," Hill showed up with a local man to save him--she launched many bazooka rounds on Osborn and laid down cover fire for the local to grab Thor. Maria Hill was also instrumental in the fight against Osborn. These actions by Hill during Siege did not go unnoticed--Captain America eventually appointed her to lead a new team of Avengers. (Click on the highlighted names above to learn about the place, event, character, and/or team.)
More recently, Captain America decided to reactivate S.H.I.E.L.D. with Daisy Johnson as the new director and Maria Hill again in the charge of deputy director. (To learn about Quake, click on the highlighted name above.)
To learn a little bit more about Maria Hill, click on the following link, http://marvel.com/universe/Hill,_Maria.