the kind of radiation you mentioned here; what is it actually?
In physics, electromagnetic radiation refers to the waves of the electromagnetic field, propagating through space, carrying electromagnetic radiant energy.
Electromagnetic radiation
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. 
how does the redshift show galaxies are moving away from us If a source of the light is moving away from an observer, then redshift occurs; if the source moves towards the observer, then blueshift occurs. what is meant by this red term? In physics, redshift is a phenomenon where electromagnetic radiation (such as light) from an object undergoes an increase in wavelength.
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Electromagnetic radiation [SEP] Introduction
In physics, electromagnetic radiation (EM radiation or EMR) refers to the waves (or their quanta, photons) of the electromagnetic field, propagating (radiating) through space, carrying electromagnetic radiant energy. It includes radio waves, microwaves, infrared, (visible) light, ultraviolet, X-rays, and gamma rays. Classically, electromagnetic radiation consists of electromagnetic waves, which are synchronized oscillations of electric and magnetic fields. In a vacuum, electromagnetic waves travel at the speed of light, commonly denoted "c". In homogeneous, isotropic media, the oscillations of the two fields are perpendicular to each other and perpendicular to the direction of energy and wave propagation, forming a transverse wave.