What is intoductrion

1 the act or process of introducing or process of being introduced. 2 a presentation of one person to another or others. 3 a section at the beginning of a book which explains briefly what it is about, why it was written, etc. 4 a book which outlines the basic principles of a subject, suitable for beginners. 5 a short passage of music beginning a piece or song, or leading up to a movement. 6 something which has been introduced.
Chambers | Free English Dictionary (http://www.chambersharrap.co.uk/chambers/features/chref/chref.py/main?title=21st&query=introduction)