As the star rotates radio waves produced by hot gas in the atmosphere is channeled by the magnetic field. Charged particles, accelerated by the magnetism of the neutron star, flow along the magnetic field lines, producing radio radiation that beams outward. The pulsar forms a rotating radio beam - this is the lighthouse effect. If the earth is in the path of the beam then with every sweep of the beam we catch a pulse of the pulsar. So far more than 350 pulsars have been found.
Pulsars make incredibly accurate clocks.
Each pulse repeats itself with a timing that is better than one part in a million. Most pulses repeat on the order of a second. These may be due to neutron star quakes where the surface cracks under the enormous gravity. This happens because the pulsar is losing rotational energy as it emits energy. The Crab Nebula - a great example.