Extraction is the process of pulling one or more products out of another by a liquid extractant.  

This can be by liquid extractant from another liquid, L/L extraction, or

it can be by liquid extractant from solids, S/L extraction.

There are many types of different equipments used for extraction and each process has an optimum organic solvent or solvent mixture.

Processes can be continuous and batch, depending on the capacities and extraction kinetics.

In addition to organic solvents, in recent years clean Super Critical Fluids have become more and more popular.  Mostly used in Carbon Dioxide CO2.  At high enough pressures and temperatures, the CO2 becomes super critical allowing clean batch extraction.  Once the temperature and pressure are reduced to atmospheric the CO2 evaporates and the extracted product is pure and free of any solvent traces.  Very suitable for pharmaceuticals and neutraceuticals for human consumption.