What is shale gas and how will the fracking process work?

Fracking (hydraulic fracturing) is the process of of drilling down into the earth to release the shale gas stored underground that can be used to power our homes.
It’s controversial because on on hand, it means the UK can produce more of it’s own gas and not rely on foreign imports, but there have been questions raised about its safety, with some claiming it could cause earthquakes and contaminate water.
But what is shale gas and how would the fracking process work? This video explains: