Short answers, pulled from the story.
Agamemnon was the king of Mycenae who commanded the combined Achaean forces during the Trojan War. He was the son of King Atreus and Queen Aerope, the brother of Menelaus, the husband of Clytemnestra, and the father of Iphigenia, Electra, Orestes, and Chrysothemis, among others.
Agamemnon was killed upon his return from Troy. In the oldest versions, Aegisthus ambushed and killed him at a feast. In the account given by Pindar and Aeschylus in the Oresteia, Clytemnestra killed him in a bath after trapping him in a net or blanket so he could not resist. Clytemnestra's stated motivations included revenge for the sacrifice of their daughter Iphigenia and jealousy over his war prize Cassandra.
Agamemnon sacrificed his daughter Iphigenia to appease the goddess Artemis, whose anger had halted the Greek fleet at Aulis with plague and windless seas. The prophet Calchas declared that only Iphigenia's death could lift the goddess's wrath and allow the ships to sail for Troy. Some versions, including Euripides' Iphigenia at Aulis, say Artemis substituted a deer at the last moment and spirited Iphigenia away to Tauris.
The curse on the House of Atreus began with Agamemnon's great-grandfather Tantalus, who was punished by Zeus for feeding his son Pelops to the gods and stealing ambrosia. It deepened when Pelops killed a charioteer named Myrtilus, who cursed Pelops and all his descendants before dying. The curse expressed itself across generations through murder, incest, and betrayal, ending only when Orestes was acquitted before a divine tribunal in Aeschylus's Oresteia.
Agamemnon served as commander-in-chief of the Greek forces and is portrayed as a representative of kingly authority. His quarrel with Achilles over the captive Briseis drives the central conflict of the Iliad, as Achilles' withdrawal from battle brings disaster upon the Greeks. Agamemnon also has an aristeia in Book Eleven, a day of exceptional battlefield glory comparable to Achilles' own aristeia in Book Twenty-one.
Several etymologies have been proposed. One interprets the name as meaning "very steadfast" or "resolute," from Greek elements meaning "very much" and "to stand fast." Another reading yields "very mindful" by connecting the second element to a word for "to think on" or "to provide for." Linguist Vaclav Blazek has also proposed a link to the Vedic Sanskrit word Agni on etymological and functional grounds.