Many of the things we use are dug from the ground. The people who dig them are miners and quarrymen.
In some cases only a few people are needed, but in the case of coal mines, very large numbers of people were needed and whole cities have grown up around coal mines.
Rock, metal and coal dug from mines are heavy, so factories using these materials are often built close to mines. In this way only a little money has to be spent on carrying the materials between mines and factories.
