What does contribution to a resonance structure mean?

[Mohamed Mido]

In the textbook, I see the phrase "contribution to a resonance structure" a lot and I don't quite understand what it means. Does it mean which is the most preferred structure or something else?

[Faith St Amant 3D]

A resonance hybrid is the blending together of all the possible resonance structures for a molecule, so each possible resonance structure "contributes" to the blended version to a certain degree. We can look at the observed bond lengths and the expected bond lengths to get a rough idea of which resonance structures contribute to the hybrid more than others. That's the way that I understand the term, but there could be a more exact definition. Hope this helps!