Normally, when people say, "Show, don't tell," they're talking about exposition.
But it's possible to do an even worse job, by including an "Author's note." Not a footnote, even, just a giant sink-hole in the middle of the story that will suck in the reader's suspension of disbelief and replace it with the screeching tires and crashing metal of a head-on collision between the author's enthusiasm and the reader's immersion.
Picture this: there's a guy, and another guy, and a bunch of girls. One guy is a professional race-car driver on the NASCAR circuit. Thus:
"We were brainstorming, trying to come up with ways to help raise money for the NASCAR Foundation," he explained.
[Author's note: the NASCAR Foundation is a charitable organization that raises money to support multiple charities, especially those helping children.]
Now, that's an example of what not to do. And here are some ways to not do it:
"We were brainstorming, trying to come up with ways to help raise money for the NASCAR Foundation," he explained. "The NASCAR Foundation is a charitable organization that raises money to support multiple charities, especially those helping children."
That wasn't quite pure exposition, since at least it was in a character's voice.
Or:
"We were brainstorming, trying to come up with ways to help raise money for the NASCAR Foundation - the NASCAR charitable organization," he explained.
Or:
"We were brainstorming, trying to come up with ways to help raise money for the NASCAR charity foundation," he explained.
Or:
"We were brainstorming, trying to come up with ways to help raise money for the NASCAR Foundation," he explained.
"What's that?" asked SomeGirl.
"That's the official charity of stock car racing, it's sponsored by NASCAR and run by them," he said.
This was kind of a low-hanging fruit, in that the telling is really obvious, and the showing too easy. But seriously, if you think about breaking the fourth wall to address the reader because they might not know something, then just have your dumbest character about the subject ask the question that you're afraid the reader might ask, and answer it within the story.