What is groundwater? What are the sources of water which are fed by groundwater?

Water found below the water table is called groundwater.

The sources of Groundwater is:

The rainwater and water from other sources such as rivers and ponds. These seeps through the soil and fills the empty spaces and cracks deep below the ground by the process of infiltration. The groundwater, thus, gets recharged by this process. At places, the groundwater is stored between layers of hard rock below the water table also known as an aquifer. Water in the aquifers can be usually pumped out with the help of tube wells or hand pumps.