Things that are profitable make money or are beneficial in other ways. Businesses hope to be profitable in the financial sense, but a profitable relationship is one that's good for everyone involved.
Profitable started out as a word to describe anything useful, but it hooked up with finance in the mid-1700s. Profits are measured in money earned beyond expenses, so profitable businesses or transactions make money. A busy restaurant, sold-out concert, and best-selling book are all profitable. People also use this word for situations that are good in ways that don’t involve money. If you learned a lot from something, then it was a profitable experience, even if you didn't make any cash.