An example is a particular instance of something that is representative of a group, or an illustration of something that's been generally described.
Example comes from the Latin word for "specimen." If you want an example of mainstream teen fashion, find a 13-year old in a mall. If you set a good example, then you show your peers how they should behave. But if you’re an unrepentant criminal and you keep getting in trouble, a judge might give you a really long prison sentence, as an example to other unrepentant criminals out there.