According to Wikipedia (May 2020):
Craic (/kræk/ KRAK) or crack is a term for news, gossip, fun, entertainment, and enjoyable conversation, particularly prominent in Ireland. It is often used with the definite article – the craic – as in the expression "What's the craic?" (meaning "How are you?" or "What's happening?").
BTW, I personally prefer the spelling crack but nowadays it tends to get confused with some manner of recreational pharmacology. I tend to use both as the mood takes me.
Scroll down and you’ll get the gist of what craic/crack is.
Photo: Art installation, Salt Lake City.