What is the difference between protons and neutrons

- - A proton has a positive electrical charge. A neutron has no charge.

- - Their masses are slightly slightly slightly different. I don't remember which one of them is slightly slightly more massive. The thing that blows my mind is wondering HOW you would go about measuring the mass of either one, and HOW to do it so accurately that you can tell the difference between them, which is much less than 1%. Those scientists are cool and amazing guys.