From WoW-Quest.NET

A repeatable quest is a quest that can be done more than once, usually in the form of dailies, however only 25 repeatable quests can be done in one day.

Types

• Daily quests are quests you can do everyday and reset at 3am server time.
• Weekly quests are quests you may do once or twice a quest as they reset every 5 days and on tuesday.
• While not true repeatable quests the seasonal event quests are usually reset each year making them yearlies.