Help me understand word "tangential" I no understand

Source: Vocabulary.com

"Tangential describes something that's not part of the whole. If you make a comment that is tangential to the story you're telling, it's a digression. The story could still be understood without it.

In geometry, a tangent is a line that touches a curve in one spot but doesn't intersect it anywhere else. Tangential means something that goes off in one direction that way and doesn't return. People can feel tangential — as though they're inessential and not relevant to a larger group"

I'm confused of word's meaning. Many meanings for this word like 'slightly connected or touching upon; incidental; peripheral' and 'superficially relevant; digressive or divergent' I want help please