How to add small popup when text is hovered/clicked on?

To either define a word or phrase, say a brief description, or introduce a new concept that isn't common knowledge, I want to add this as a feature that Squarespace already has on their own Help Articles.

I would assume this would take Javascript to pull off, but my knowledge is limited. There are several of these unanswered questions on this forum, so I'm just adding myself as another voice for the desire to be able to do this.

Thanks in advance for any pointers!