Question

What is a resonance structure?

Answer 1

A resonance structure has delocalized electrons

Explanation:

Resonance structures have two or more possible electron structures. Often, they are showed with dotted lines or two+ structures with an arrow between them.

The electrons distribute themselves evenly between both configurations (probability-wise) so that what we end up is roughly an "average".

This is a good example of resonance.
[http://chemistry.stackexchange.com/questions/8868/benzene-and-resonance]

Here is the unhelpful technical definition: "The idea of resonance is that the actual molecule is a definite structure that is a hybrid of two theoretical structures"