Apollo was an oracular god, as he was the prophetic deity in the Oracle in Delphi. People from all over the known world travelled there to learn what the future held for them, through his priestess Pythia. The god was also worshipped in the island of Delos, which was initially dedicated to his twin sister Artemis. In relation to the rituals and practices that took place in Delos and Delphi, it could be said that there were two completely distinct cults in honour of Apollo.
As already mentioned, Apollo was also considered as the god of healing and medicine, either through himself or through his son Asclepius. At the same time, he could also bring forth disease and plague with his arrows; it was considered that a god that can cause disease is also able to prevent it.