Einstein's general relativity says gravity is spacetime curvature, but what does that mean? Let's take a look at how gravitational time dilation results in a...
It’s just meant as a physical analogue to demonstrate some features (namely how the shape of the sheet/gravity affects things that travel on/through it) in a way that people can understand easily.
This is a pretty accessible visualization of gravity.
https://youtu.be/b9XhexlQMZw
But it’s kind of a terrible one, because it uses gravity to explain gravity.
It’s just meant as a physical analogue to demonstrate some features (namely how the shape of the sheet/gravity affects things that travel on/through it) in a way that people can understand easily.
If it’s the demonstration I’m thinking of, it uses gravity to visualise the affects of an otherwise invisible force.