The prototype of this document, originally written by Ales Hvezda for gEDA/gaf, you can find at http://wiki.geda-project.org/geda:master_attributes_list
Attributes in Lepton EDA is the way to provide specific information about schematics as well as components and nets used in it. The information is then processed by Lepton tools to make it available for using in various workflows such as, e.g., SPICE simulation or PCB creation.
Note: Unlike geda-gaf, Lepton EDA supports attributes with empty values. See Attribute compatibility for other improvements in attribute support.