What exactly is an embargo for a journal?

I was trying to access this article and was told this journal is "embargoed" for more than a year. This is the first time I have seen the term embargo used in an academic setting.

This answer talks a bit about the idea of journal embargoes. Wikipedia has more information but I do not find it helpful at all.

As I read (on Wikipedia), it seems embargoes in journals are for future stories (and not for everything ever published). The article that I am seeking is from two years ago.

This question implies that embargoes deal with the relationship between publisher and author, which does not make sense in the context of my request.

This answer implies that embargoes are about limiting access electronically, but, again, it seems I can buy the article for $40 so clearly it is available electronically.

So, what exactly is an embargo (in this context)? Does it really mean that I simply have no access to this through my university account? It looks like it is available to the general public (if you pay) but not to those of us with access through university subscriptions.