The Higgs boson gives elementary particles their mass, but 98% of the visible mass in the Universe (not dark matter) comes from a less famous mechanism: chiral symmetry breaking. This is why protons and neutrons are so much heavier than their quarks!

Briefly, protons and neutrons act like bags full of a soup of virtual quark-antiquark pairs, which give them most of their mass. This soup, called a 'quark condensate', breaks a certain symmetry that exists outside the bag: 'chiral symmetry', where you change the phase of the clockwise and counterclockwise rotating quarks separately. In the quark condensate, the clockwise spinning virtual quarks are entangled with counterclockwise spinning virtual antiquarks.

https://en.wikipedia.org/wiki/Chiral_symmetry_breaking

Chiral symmetry breaking - Wikipedia

@johncarlosbaez Something just occurred to me. I've seen that description of the proton (and neutron, too, I guess) as three quarks, plus a lot of gluons, and virtual particles popping in and out of existence. The cloud of virtual particles is mostly confined to the diameter of the proton. What is it about this environment (the “bag of soup” 😊) that causes a higher number of virtual particles to appear, compared to a volume of space that *isn’t* a proton (i.e. "empty” space)?