Volume, Panning and EQ- Why and how is it used?

Volume- 

This is the first step in the Mixing Process in which you need to ensure that each instrument in your studio recording is audible. This may mean turning down the volume of some instruments as well as turning up the volume of others. Changes to EQ and effects throughout the rest of the mixing process may mean that you will have to adjust the volume again at some points.  

Panning- 

This is the second step in the Mixing Process, Panning helps us to achieve a balanced and interesting stereo image. This means that we can ensure that there isn't too much instrumentation going on in one ear in comparison to the other. For example, if most of the drum track was panned towards the left then you may wish to pan another instrument such as an electric guitar to the right in order to create a balance and prevent the left side from becoming too heavy and jumbled with sound. Like volume, you may end up going back 

EQ- 

EQ can be used both creatively and remedially either to improve and/or to alter creatively the sound of an instrument. For example, you can boost the low frequencies in a vocal part in order to give more of a 'booming' tone to their voice. You can also use EQ to reduce any flaws in the sound of the recording, such as any 'twanging' qualities of a guitar or to reduce background noise picked up from the recording environment, such as the sound of air conditioning.