Lichens are mutualistic associations between some species of fungi (usually ascomycetes) and algae (mainly green algae and cyanobacteria). In these associations, fungi are called mycobionts, and algae, which are photosynthetic organisms, are photobionts.
The scientific name of lichen is the scientific name of the fungus present in the association.
"If I've understood it right, the yellow ones are those that stay up longest without changing. And maybe in a short time from now a planetary system will form around it too." Italo Calvino - As long as the sun lasts.