Ontology Development 101: A Guide to Creating Your First Ontology

I am a couple of weeks in on my graduate course that focuses on social media & informatics. While I already posted something about ontologies and folksonomies, I stumbled across this interesting link:

What is an ontology and why we need it (stanford.edu)

I have a general idea of the definition of an ontology based on my notes from a recent lecture- a common vocabulary for users who need/want to share information in a specific domain. At first, this did not make sense to me. I tried to learn more about different ontologies saw this wonderful graphic.

Wine drinkers/makers have their own language! Now this is something that I can relate to. After seeing this, things began to click- most disciplines have their own, common vocabulary. One thing I do not understand, if this is the case, why is that some ontologies are not recognized? Is it because they are not standardized? As a former musician (thank you health issues for destroying that career), there are a many common words we use to communicate- are these considered ontologies?