Taken literally, it’s when a person takes an action or says something -- the “signal” -- based on some principle -- the “virtue”. I think when it’s used as a pejorative (“this is just virtue signaling”), it’s being called out as disingenuous in some way. For example, if a fossil fuel company publicizes work they did to remove carbon from the atmosphere but doesn’t talk about (or even calculate) how much carbon they introduced. I could see someone calling that “just virtue signaling”.

I’m sure there are many other examples but that’s generally how I understand it. I don’t intend for my example to reflect any specific event in the past, if that matters (ie. “I made it up”). Hope that helps.

Do you recognize "self-promotion" as a kind of behavior people do, that makes their recommendations less reliable for you than recommendations from uninterested people? Virtue signalling is another kind of motivated speech where the speaker may be sincere but doesn't acknowledge their own self-interest. They gain status from professing to believe more extreme forms of socially approved views.

The benign form of virtue signalling is something like publicly mourning for a while after your spouse dies so other people understand you aren't a sociopath. The runaway form of it is jumping on your spouse's funeral pyre because it shows you are more devoted than anyone else. Or in this case burning up your company's profits on unnecessary taxpaying to show you are wealthy/socialist enough to do that.