Who is Chryseis ? How does a conflict start concerning her ?

Chryseis is the daughter of a priest of Apollo who is
taken as a concubine by Agamemnon when the Greek army conquered the city of Thebe. Her
father, Chryses, goes to Troy to beg Agamemnon for his daughter's release, bringing with
him a large ransom for her release. Agamemnon refuses to release Chryseis and sends her
father home without her. Chryses prays to Apollo for help in getting his daughter back,
and Apollo sends a plague down upon the Greek army, causing many of their men to die.
The leaders of the Greek armies eventually go to Agamemnon, with Achilles as their
spokesman. Achilles tells Agamemnon he will receive more than his share of the spoils of
the Trojan War after the Greeks defeat them if Agamemnon allows Chryseis to go home.
Agamemnon angrily agrees, but instead of waiting until after they defeat the Trojans, he
takes the concubine of Achilles, causing Achilles to pull out of the
war.