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An older version

I am an experimental particle physicist. Particle physics aims at deciphering the laws of the universe at the most fundamental level, and concerns the questions such as what our universe is made of, what their characteristics are, and how they interact with each other to constitute the universe as it is now.

Present knowledge on particle physics is concisely summarized as the standard model of particle physics. It includes six species of quarks and six species of leptons as matter particles. They interact with each other under four kinds of fundamental interactions, namely the strong, electromagnetic, weak and gravitational. The standard model accounts for the three of the four interactions (gravity is the exception).

The classical view of the interactions is via the fields. For example, the electromagnetic force acts between charged particles (e.g. electrons), and it is because a charged particle creates electric and magnetic fields around it, and another charged particle feels the force when it is located where the fields exist.
The particle (quantum) view is different from it. There exists a particle of the electromagnetic fields, and it is the quantum of light and is called the photon. The charged particles feels the electromagnetic force by exchanging the photon, the particle of the electromagnetic force, between them. In other words, the photon is the carrier of the electromagnetic interaction. Similarly, there exist the carrier particles of the other forces. They are collectively called the gauge bosons.
So the interactions between the matter particles are mediated by the gauge bosons.

The standard model is formulated as quantum field theory, which enables us to describe the physical processes such as creation and annihilation of particles and provides quantitative predictions on observables such as scattering cross sections.

Technically speaking, this "predictability" stems from gauge symmetry and renormalizability of the field theory. Gauge symmetry dictates and uniquely determines the form of the interactions that the matter particles undergo. It also is a basis for renormalizability of the theory, and without it the theory loses the predicting power.

The electromagnetic interaction (Maxwell's equations) possesses a gauge symmetry. And its quantum version, quantum electrodynamics (QED), is a renormalizable theory. The quantum field theories for the strong and weak interactions are built along the lines, and are equally successful in describing experimental results.
However, there is one notable difference. In order for gauge symmetry to hold for a theory, the mass of the corresponding gauge boson has to be exactly zero. It is fine for the electromagnetic interaction, because the mass of the photon is zero within experimental precision. On the other hand, the W and Z bosons, the carriers of the weak interaction, are very massive, some 80 and 90 times the mass of the proton, far from zero, so they would violate gauge symmetry.

This causes a dilenma. Do you give up gauge symmetry and lose predicting power? Or, do you give up massive gauge bosons?

Here is where the Higgs field comes in. It miraculously saves gauge symmetry (in a hidden way) while giving masses to the W and Z bosons. Furthermore, the same Higgs field gives masses to the matter particles as well, to the quarks and leptons.

What kind of particle is the Higgs, by the way? Is it a matter particle? A gauge boson? Neither is the answer. It is the particle of vacuum. The word vacuum is defined as space devoid of matter. Sure, there may exist no matter particles in vacuum, but it is anything but nothing. Our vacuum is thought to be filled with the Higgs field, and from time to time the Higgs particle pops up from there.

A particle consistent with the standard model Higgs particle has been recently discoverd. It is currently under the extensive studies by many physicists in the world. Why? It is because there is no other particle like the Higgs. It certainly has given us new meaning to vacuum. Also because of its relevance to the fundamentals of the theory. And because many believe the particle holds keys to possible new laws beyond the standard model.