Most people know of Apollo only as a sun god, but he's much more. Apollo, sometimes called Phoebus with or without Apollo, is a Greek and Roman god with many, and sometimes conflicting attributes. He is a patron of intellectual pursuits, the arts, and prophesy. He leads the Muses, for which reason he is called Apollo Musagetes. Apollo is sometimes called Apollo Smitheus. It is thought that this refers to a connection between Apollo and mice, which makes sense since Apollo shoots plague arrows to punish disrespectful humans.
There is much to say about Apollo. If he's unfamiliar, start with the glossary entry on Apollo.

Public Domain. Courtesy of Wikipedia.Thomas Bulfinch retells the story of the love affair between Apollo and Hyacinth(us). The pair were playing a game with a pointed missile Bulfinch calls a quoit. It accidentally struck Hyacinth, possibly because of the mischievous West Wind. When he died, Apollo made the flower called hyacinth grow from his blood.
Apollo is usually thought of today as a sun god. Here is a list of other sun gods and goddesses from mythology.

Public Domain. Courtesy of WikipediaZeus fathered both Hermes (the Roman Mercury)and Apollo. When Hermes was still a baby and Apollo grown, Hermes started rustling Apollo's cattle. Apollo knew Hermes was responsible. Zeus helped smooth out the ruffled family feathers. Later, Apollo and Hermes made various exchanges of property so that although Apollo was the god of music, he tended to play instruments Hermes had invented.
Apollo's most famous son was the healer Asclepius, but when Asclepius raised people from the dead, Zeus killed him. Apollo was furious and got revenge, but he had to pay for it with a term on Earth as herdsman for King Admetus.
Also see Alcestis
This list of titles of Apollo gives an idea of the diversity of Apollo's powers and spheres of influence.