Question

A particle which has zero rest mass and nonzero energy and momentum

Answer 1

Zero rest mass means when the particle is at rest, it's mass is zero. For example, photon has zero rest mass, means practically it has no mass. But, since photon is not at rest, it has finite energy hv.

Particles with mass cannot achieve light speed. Mass less particles always travel at light speed, or else we could not detect them.