The reason why fundamental particles have non-zero masses is still an open question in physics. The masses of fundamental particles, such as electrons, quarks, and neutrinos, arise from their interactions with the Higgs field. According to the Standard Model of particle physics, the Higgs field permeates all of space and gives mass to particles that interact with it.
The Higgs mechanism proposes that particles acquire mass through their interaction with the Higgs field, which is mediated by the Higgs boson. The Higgs field is believed to have a non-zero value throughout the universe, and particles "feel" this field as they move through it. The strength of the interaction determines the mass of the particle. Particles that interact more strongly with the Higgs field have higher masses, while particles that interact weakly or not at all have lower masses or are massless.
The masses of fundamental particles differ from those of ordinary matter, such as atoms and molecules, in several ways. Fundamental particles are considered point-like entities with no internal structure, while ordinary matter consists of composite particles, such as protons and neutrons, which are made up of quarks bound together by the strong nuclear force. The masses of composite particles, like protons and neutrons, arise from the combined masses of the constituent quarks and the binding energy that holds them together.
Furthermore, the masses of fundamental particles are typically much smaller than the masses of composite particles. For example, the mass of an electron is about 0.000000000000000000000000000091 kilograms, while the mass of a proton is about 0.00000000000000000000000167 kilograms. This large disparity in masses arises from the fact that the masses of composite particles result from the collective contributions of multiple fundamental particles and the binding energy.
It is important to note that our understanding of the fundamental nature of particles and their masses is still an active area of research in physics. The quest to understand the origins of mass and why particles have the masses they do is one of the ongoing pursuits of theoretical and experimental physicists.