Induction is a type of logic that operates by taking many specific examples and using them to draw a general conclusion. There are two types of induction, complete and incomplete. In the case of complete induction, you must survey every single possible example before coming to a conclusion. An example of complete induction would be the following:
All of the Brontë sisters were talented writers. Their first publication was a collaboration, a volume of poems to which all three sisters contributed, published pseudonymously as Poems, by Currer, Ellis and Acton Bell. Charlotte went on to write four novels, Jane Eyre, Shirley, Villette, and The Professor. Emily also wrote one of the most important novels of the nineteenth century, Wuthering Heights. Anne wrote Agnes Grey and The Tenant of Wildfell Hall. Perhaps no single family is more responsible for the development of the Victorian novel.
Incomplete induction deals with topics on which a complete induction would be impossible due to the sheer volume of information available. For example, if you wanted to prove that fast food was unhealthy, you couldn't just list all of the nutritional content in every single item in every fast food restaurant in your town. Instead, you might choose a balanced group of examples, such as one popular menu item from a taco restaurant, one from a burger restaurant, and one from a pizza place, analyze each of them, and from that draw the conclusion that many of the fast food items students eat are unhealthy.