Distillation in a kitchen is not much different that distilling in a laboratory. In the fact the process is the same, separating the component substances from liquid mixtures by selective vaporization and condensation.
Distillation may result in essentially complete separation where you have a nearly pure substance, or a partial separation depending on your application. In either case the process exploits differences in the volatility of mixture’s components and flavors and concentration.
When it comes to making an essence or concentrating flavors you have two options, one is do it yourself or two, buy the finished product as an essence. In this case the chef does it himself by way of heat, evaporation, (vacuum) and via condensation you capture the liquid in a flask.
Here are some tools you can use to achieve extraction and concentration of flavor.