Great article, well explained and not hard to follow.

https://cosmosmagazine.com/mathematics/some-infinities-are-bigger-than-others

You can also see a linked video: https://youtu.be/Uj3_KqkI9Zo

*Some infinities are bigger than others*
There are two types of infinity, and it doesn’t stop there.

"Few numbers have exercised more fascination, and confusion, than infinity. I can remember asking my father at a young age whether space went on forever. He replied that this must be so because, however far you travelled into space, you could always stretch out your arm into a void beyond.

Same thing with time: will it go on for all eternity, and does it stretch back infinitely far into the past?

Philosophers and scientists have wrestled with these questions throughout the ages, but for most of that time ‘infinity’ as a concept was not well-defined. "