How do the avalanches of photons in a laser beam differ from?

In a laser beam, all the photons emitted are exactly in same phase, but in an incandescent lamp photons emitted may or may not be monochromatic but they are not in phase.
If an photon emitted by a source is assumed to be a wave then phase difference is the difference in wavelength between the photons emitted by the source, if the phase difference is zero or integral multiples of 2*pi, then the two photons are said to be in phase.
In laser all the emitted photons are in phase
Its not true in incandescent bulb
Moreover in an incandescent bulb photons are emitted by heating the filament to incandescence (heating it to temperature at which it emits photons)
but in laser devices photons are produced by stimulated emission, hence laser gets is expansion as Light Amplification by STIMULATED EMISSION of Radiation.
In stimulated emission, an atom in an excited state(meta stable) is brought down to ground state by external agencies resulting in the emission of photons

Light emitted by a common lamp (incandescent) is incoherent, that is, photons of many frequencies and in many phases of vibration are emitted.  The beam spreads and becomes weaker with increased distance.  A laser is a device that produces a beam of coherent light.  A beam of coherent light spreads and weakens very little.