Even Greener Pastures

Could you explain the meaning of 'oxymoron' please and give some examples?  = > a combination of incongruous?

For example, Sergey Polunin, whose video dancing I posted recently, is a classic ballet dancer  but he has eight tattoos, which is considered to be out of norm and rather unexpected.
 
Thank you

I have never thought of things like that video as oxymorons because I thought oxymorons strictly relate to the words themselves.  I have never used the word ¨oxymoron¨ to describe situations or people, just phrases.

The famous one is „flaming snowballs.“