The answer to the question really depends on where you live as cider can be different things in different places. Here in East Devon it is generally made from traditional varieties of apples, rejoicing in names like Slack-me-girdle and Sweet Alford. These are not like eating apples, they are generally sour but are perfect for cider making.
The natural sugars in the apples ferment at lower temperatures than those needed for wine making. The farmers collect the apples, store them for a while, then mince them up and make them into ‘cakes’ of apple pulp. These are then put into cloths and stacked into what is known as a cheese. The cheese is then pressed to extract the apple juice.
Once all the juice has been pressed out of the apple pulp it’s put into oak barrels and left to ferment. The barrels are stored in a stone building, where the juice ferments slowly over the winter. In the spring it’s racked off into different barrels to remove all the impurities and dead yeast. It continues fermenting in the new barrels until all the sugars are used up. It's now ready to drink but it’s quite often kept for another two or three years to improve the flavours.
In other parts of the world it is simply concentrated apple juice. In Normandy it is distilled into something much stronger -
Calvados
There are still farms in East Devon where they make their own farmhouse scrumpy, but most production is done in factory conditions. The Lyme Bay Winery is a superb example of a small factory producing traditional ciders and wines. They produce three types: Jack Ratt Scrumpy, Jack Ratt Vintage and Lyme Bay. Why not pay them a visit and sample them for yourself?