• A set of recommendations for text encoding, covering both generic text structures and some highly specific areas based on (but not limited by) existing practice
• A very large collection of element definitions combined into a very loose document type declaration
• A mechanism for creating multiple views (schemas) derived from the foregoing
• One such view and associated tutorial: TEI Lite (http://www.tei-c.org/TEI/Lite/)

for the full picture see http://www.tei-c.org/TEI/Guidelines/