Promotion of anything at all is advertising, with or without compensation. The word advertising is pretty well defined, and the dictionary definitions don’t usually mention compensation, e.g. https://www.merriam-webster.com/dictionary/advertise.

An example I’m sure you would consider advertising - consider Google advertising Google Fiber in Google search results, or Facebook advertising business services on Facebook, or Apple, Netflix, Cinemark advertising their own shows & products in their own channels. You’ve seen lots of these, I’m sure you would consider them ads, but it’s not the compensation that makes them ads.