Question: what is gravity?

Dominic Doyle answered on 14 Mar 2017:

It’s the most important of the fundamental forces.
But it is the weakest and works over the longest distances.
It holds the universe together and keeps us on the Earth and in orbit around the Sun.
There are three other fundamental forces;
Electromagnetic – e.g. magnetic field
Strong Nuclear
Weak Nuclear
See here for more details
https://en.wikipedia.org/wiki/Fundamental_interaction