Wikipedia is a multilingual, web-based, free-content encyclopedia project based on an openly editable model. The name "Wikipedia" is a portmanteau of the words wiki (a technology for creating collaborative websites, from the Hawaiian word wiki, meaning "quick") and encyclopedia. Wikipedia's articles provide links to guide the user to related pages with additional information. Wikipedia is written collaboratively by largely anonymous Internet volunteers who write without pay. Anyone with Internet access can write and make changes to Wikipedia articles." - Wikipedia
A tertiary source is one that synthesizes content from primary and secondary sources to provide an overview of a topic. Generally, tertiary resources package information in an easy-to-understand or convienient format. Examples of tertiary sources include:
Tertiary sources are not usually accepted as appropriate sources for college level work. However, these types of sources are an excellent starting point for research or if one needs a quick and general overview of a topic.