Terms & terminologies related to borewell: A layman's attempt to demystify the same

I am planning to construct a borewell for agricultural purposes. When I consult with others they mention that discharge / quantity of water (in inches) is vital in selecting a pump for the borewell. Could you please explain in layman's language what the discharge/quantity of water in inches exactly is, and how to calculate the same.

This will help me to decide on a pump vendor & also help in understanding the situation better.

Sohan Mangar