Emulsions are water-based, with vinyl or acrylic resins added to make them more hard-wearing.
In general as the shine increases, the paint tends to be more hard wearing.
Vinyl silk emulsion gives a high sheen finish and is the most durable of all the emulsion paints.
Some manufactures make specific Kitchen & Bathroom paint which is ideal for areas of high humidity (e.g. Dulux Kitchens and Bathrooms)