It's a group of micro organism that eat rocks. You have heard lichen they are a species of endolith.

Endo in Latin is: inside or within e.g endoscope (though you can look that up if you don't know 😁)

Lith is stone like the Lith in lithograph as they a stone for printing.

The blobs on the rocks are actually the endoliths they are consuming the rocks but to us it's a slow process.