A) Howard Stark was a brilliant inventor and businessman and the father of Tony Stark/Iron Man. He founded Stark Industries and was one of the founders of SHIELD. During WWII he worked on various government projects, including the Manhattan Project and "Project: Rebirth". Howard also helped the Strategic Scientific Reserve fight against HYDRA. He constructed Captain America's shield and helped make an upgraded suit for him. In 1991, he and his wife were killed by HYDRA agents, who made it look like a car accident.
B) Margaret "Peggy" Carter was a British officer representing the Strategic Scientific Reserve and Steve Rogers's World War II girlfriend. After the war, Agent Carter secretly assisted Howard Stark, who found himself framed for supplying deadly weapons on the black market. She was assisted by Stark's butler Edwin Jarvis. They found those responsible and disposed of the weapons which led to the mysterious organization Leviathan. Peggy, along with Howard, founded S.H.I.E.L.D. with Colonel Chester Phillips. She was still alive during the events of Captain America: The Winter Soldier, though bedridden and in poor health due to her old age.
In 1989, Howard, Peggy Carter and Mitchell Carson were having a meeting in the Triskelion, when Hank Pym confronted him about S.H.I.E.L.D.'s attempts to replicate the Pym Particles. Peggy was shocked at the discovery; Howard attempted to justify the decision due to the applications of the particle and Carson noted the military benefits. Hank vowed to take the secret of the Pym Particles to his grave.
C) Sam Wilson is an ex-military officer and friend of Steve Rogers. Wilson aided Rogers and Black Widow when they took down a compromised S.H.I.E.L.D. Wilson is now a member of the new Avengers under the codename Falcon.
While training at the New Avengers Facility, Wilson detected an intruder in the base and decided to investigate. Flying onto the roof, Wilson spotting a man wearing a suit that seemed to make him the size of an Ant. Once it was made clear that Wilson could see this man despite his tiny size, the man regrow to normal height and introduced himself as Scott with the code-name Ant-Man, noting that he was a big fan of Falcon and the Avengers. Wilson demanded to know why Ant-Man was in the facility but the man claimed to simply be needing to borrow a device from them.
Believing that Ant-Man was a sort of spy, they began fighting. Ant-Man managed to stop Falcon by shrinking and disabling Falcon's suit from the inside. When Falcon managed to recover from the fall, Ant-Man had already escaped with the device and Falcon was unable to track him. Wilson then said through the comm link that Captain America must never know about this embarrassing failure.
Though embarrassed, Wilson became fascinated by this new hero and his powers, having heard of him using his abilities to stop the sale of a new super-weapon called the Yellowjacket Suit. Believing that he could be of benefit to the Avengers, Wilson began to ask around to try and find and recruit Ant-Man for the Avengers, despite only knowing his frist name to be Scott. Eventually Wilson became close to finding him through the friend of a friend of the Ant-Man who agreed to help him.
D) Captain Steven "Steve" Grant Rogers is the only living, successful test subject of the Super Soldier Serum developed by Abraham Erskine during the Second World War. The patriotic super soldier was given the title of Captain America and fought against the Nazis and their rogue science division HYDRA. Rogers was frozen for nearly seventy years and awoke in the twenty-first century, where he joined the Avengers as their team leader. After the Battle of New York, Rogers became a S.H.I.E.L.D. agent. He went on several covert missions with agent Natasha Romanoff and S.H.I.E.L.D. counter-terrorism team. Both Rogers and Romanoff later discover that HYDRA has secretly operated within S.H.I.E.L.D. for decades. Rogers, with the help of Sam Wilson, was able to destroy HYDRA's Helicarriers for Project Insight. After the HYDRA Uprising, he went off on his own to search for his friend Bucky Barnes, with the help of Sam Wilson. In the midst of his quest, Rogers reassembled with the Avengers, working to bring down what was left of HYDRA, and made use of his leadership skills once again in the battle against the psychotic artificial intelligence, Ultron. Unlike most members of the original Avengers, Rogers remained as a member and the leader of the second incarnation of the team after the Battle of Sokovia.
E) Sergeant James Buchanan "Bucky" Barnes is the protege and childhood friend of Steve Rogers and a member of an elite special unit of Allied soldiers formed in World War II known as the Howling Commandos. He was assumed deceased after falling off of Zola's Train. Unbeknownst to the Commandos, Zola's experimentations allowed Bucky to survive the fall.HYDRA subjected him to brainwash treatment as a candidate for the "Winter Soldier" program. Under HYDRA's control, Bucky would be responsible for countless assassinations including political parties, over the next few decades. Bucky became a formidable fighter and an even more ruthless killer. His experiences with the KGB would earn him the name of The Winter Soldier. After the fall of S.H.I.E.L.D., Bucky started to remember who he was.
Sam Wilson and Steve Rogers have managed to trap the Winter Soldier in a remote location, by trapping his cybernetic arm in a vice. Rogers told Wilson that they would not inform Tony Stark of Barnes' capture, as Stark could not be trusted with the information. They then discussed recruiting him and Ant-Man, whom Wilson had recently encountered, to their team.
