Years ago it was cut by hand with a long spade type instrument called a "slane". It was like a long narrow spade. This had a piece on top for your foot to dig it in to the ground. 
The turf was the lifted out either on the slane or by some one working in tandem with the man cutting turf. I used to do this with my father in law, now deceased.
Technology took over. The peat is now dug out of the ground with an tracked excavator type machine, placed in a hopper type trailer pulled by a tractor and spread out of tubes on to flat ground. It is left to dry for a while then they all have to be stood up in little groups to dry. You then put the little groups into slightly bigger groups  until they dry. It does take a lot of work.
If you look behind the red Land Rover behind it you will see the bog from where the turf was taken by hopper and then spread in the field. 
In days gone by most people had their own section of bog to cut from. Later on some people with a lot of bog cut and spread the turf by hopper and then sold it. You bought so many "rows" or lengths of turf. It was up to you to work them i.e. get them dried and then transported home.
It is compressed vegetable material. Once removed it is not replaced.
Peat cutting and Turf cutting in Ireland - YouTube
Over-Exploitation of Peatlands for Peat - Irish Peatland Conservation CouncilIrish Peatland Conservation Council