What particles are called massless? What is their speed? How is the statement that massless particles have energy

What particles are called massless? What is their speed? How is the statement that massless particles have energy and momentum is substantiated?

Massless particles are called particles that have no rest mass. The speed of these particles is equal to the absolute speed. When massless particles interact with other particles, the laws of conservation of momentum and energy are fulfilled, which makes it possible to assert that massless particles have energy and momentum.

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