Encaustic paint is 100% pure beeswax and damar resin with added pigments.
An ancient Egyptian technique, the famous Fayum Mummy Portraits, created 1st Century A.D., were placed over a mummy as a memorial, and had impressive details of realistic facial features. Many of the Fayums have survived to today, and their color is still fresh and beautiful. The durability of encaustic is because beeswax is impervious to moisture. So they do not deteriorate, yellow, or darken.
Painting with hotwax requires heating it to 180-200F, and then heat-fusing to your substrate using a hot gun, blow torch or an iron.
There are countless techniques, materials, and ways to explore an artistic style of one's own. It is one of the fastest-growing mediums in the US, but is still mostly unknown in Europe.