Solid Floor:

Solid floors in the UK are generally constructed in layers.
1, a foundation layer of compacted hardcore (to stabilise the soil) topped with what is commonly called a blinding layer of sand, (the sand fills any gaps in the hardcore and helps to give a smooth surface)
2, then a layer or sheet of plastic to stop any moisture getting into the house, known as a damp proof membrane (DPM)
3, a layer of insulation to help keep the heat in, older floors built before 1995 generally don’t have any insulation,
4, a layer of concrete (sand, cement, aggregate) known as a sub-floor which may or may not have some sort of reinforcement in it.
5, a top layer of sand and cement known as a screed.
6, the finish or visible layer, i.e. ceramic tiles vinyl tiles, carpet