What does Kidney Reflux mean?

I just got a sonar done of my bladder, as I’ve been having bladder issues, the sonar man said, ‘Something, something is to small,’ I didn’t get the word, then after I voided he checked my kidney and said, ‘oh it’s normal, maybe it’s just reflux.’
I of course got home and checked reflux and now I“m freaking out.
What does that mean exactly, does anyone know?

I’m seeing the Urologist again but not for a week – I don’t know how to stop worrying.