Apollo is the god of the Sun, music, literature, and sometimes illness; he's the son of Leto and Zeus. He generally appears as a young man with a bow, arrows, and a lyre.
Every day, Apollo led Helios's chariot across the sky. This chariot was bright gold, and was drawn by fire-breathing horses.
He gave life to newborn children and animals, but could, and did, also spread illness.
Apollo fathered quite a few children, many of whom had prophetic powers; some have their own interesting stories. He and Thalia, a Muse, began the line of Corybantes, eccentric priests who shaved their hair to forelocks. Orpheus and his brother Linus (also musical) were born to Calliope, another Muse; Aesclepius was born to Coronis, a nymph who later dumped Apollo. Hymen, the god of marriage, was his son by Urania (a third Muse). King Aeetes of Colchis, the owner of the Golden Fleece before Jason took it back, was also one of Apollo's offspring. Ion, the founder of the Ionian people, was Apollo's long-lost son by Creusa (a human). Lastly, Aristaeus was Apollo's son by Cyrene (a nymph).
However, Apollo also had some notable failures with women, like Daphne (a nymph who turned herself into a laurel tree to avoid him); Marpessa (a woman who chose Apollo's mortal rival Idas); and Cassandra (to whom he gave the gift of prophecy - but then she broke a promise to him and was cursed to always be right but never be believed).
One of Apollo's early feats was killing the huge snake Python, who had been sent by Hera to scare his mom, Leto. In order to find priests to handle sacrifices (which admittedly must have been pretty bloody work) and priestesses to take on the job of delivering oracles, he turned into a huge dolphin and caused a ship full of worthy people to run aground. He calmed them down, telling them that he was a god and that they would be okay. Awestruck, they immediately volunteered to serve him and worship him as Apollo Delphinios, or Apollo the Dolphin.
Apollo also loved his sons, especially those with divine abilities, and would do anything to save them from harm. When Zeus killed the then-mortal Asclepius at Hades's request (Asclepius could bring the dead to life), Apollo killed the Cyclopes in retaliation, since they had forged the lightning bolt Zeus had used. For this crime, Apollo spent 9 years on Earth as a shepherd. It must be noted that Asclepius returned as a god, and the Cyclopes, being more-than-mortal, also returned to feature in other myths.