Pulsars, are rotating and radiating neutron stars and are superb astrophysical laboratories of extreme physics. A typical neutron star has radius of ∼ 10 km, magnetic field of ∼ 10^12 Gauss, density of ∼ 10^17 kg/m3, rotating at a frequency ∼ 1 Hz and has a surface gravity of ∼ 10^12m/s2. We observe pulsars as a sequence of periodic pulses mostly in the radio wavelength. What is mind-boggling is that the radio emission arises from a kilometer-sized emission patch which is at a distance of ∼ 10^19 meter from us, and yet we see it!! The equivalent blackbody temperature of this radio emission is in the range 10^25--10^30 K, which exceeds the limit for any incoherent emission process. The physical mechanism of how this emission is generated is considered as one of the most challenging problems in astrophysics.

In this talk we will discuss the first discuss the high quality radio observations
and techniques have constained the nature of the coherent radio emission. This will include constraining radio emission regions in the pulsar magnetosphere, identifying the emission with the extraordinary and ordinary plasma modes.

We will then proceed to describe the physical processes that arise around a rotating neutron star, which is a massive unipolar inductor. These processes lead to the generation of highly relativistic flow of electron-positron plasma in which we believe the radio emission is excited by a process called coherent curvature radiation.