Encaustic is the name for both a wax painting medium (beeswax and damar resin) and a painting process involving heat to apply and fuse the medium. The name Encaustic comes from the greek enkaustikos which means “to heat” or “to burn”. Heat is used throughout the encaustic painting process. Encaustic lends itself to mix media and collage, natural dried collage elements can be layered within the wax.
Here is a blog post offering a more detailed description including the History of Encaustic from The Artist’s Handbook