When something is considered infinite what does that encompass?

I am not really sure how to formulate this question but here it goes.
When calling something infinite does that include mass, time, size,
distance. Can these be defined as infinites separently? Remember when we were pretty sure the atom was as small as you could go? Then it was discovered there were quarks etc. Can smallness be infinite ( do you just end up with nothing) or is size only able to be infinitely larger? My mind locks up when I try to get my head around infinity. So Collective what is infinity?