A tutorial is a method of transferring knowledge and may be used as a part of a learning process. More interactive and specific than a book or a lecture; a tutorial seeks to teach by example and supply the information to complete a certain task.
Depending on the context a tutorial can take one of many forms, ranging from a set of instructions to complete a task to an interactive problem solving session.
Questions having the tutorial tag regards the User Experience of tutorials or the design of tutorials.
Reference: http://en.wikipedia.org/wiki/Tutorial