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How did the electroweak theory partially unify two fundamental forces?

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What is string theory? — string theory Brian Greene explains the basic idea of string theory in under three minutes.

The electroweak theory unifies the electromagnetic force and the weak force by describing them as two facets of a single, more fundamental interaction.12

Physicists Sheldon Glashow, Abdus Salam, and Steven Weinberg independently developed this framework by constructing a gauge-invariant theory that required the existence of four carrier particles, or gauge bosons. In this unified model:12
* The photon mediates the electromagnetic force and remains massless.13
* Three massive particles—the charged W particles and the neutral Z particles—mediate the weak force.12

The theory explains the apparent difference in these forces through the Higgs mechanism. While the underlying symmetry of the electroweak force is mathematically elegant, it is hidden or broken by the Higgs field, which permeates space and endows the W and Z bosons with mass, thereby limiting the range of the weak force. This unification is a cornerstone of the Standard Model of particle physics.132