What is a basic or foundation patent?

Basic patent or a foundation patent, by definition, is pioneering type of patent, such as a patent for the first laser or other comparable earthshaking technology. [1]
However in the context of thinkpat blog, patents which mark the birth of a technology, patents from which numerous citations are taken for improvement patents in the technology, are considered to be basic or foundation patents.

For example:
U.S. Patent US4063220 - 'Multipoint data communication system with collision detection' is the first patent describing Ethernet. It can be considered the basic or the foundation patent for Ethernet.

[1] http://www.tms.org/pubs/journals/JOM/matters/matters-9501.html
[2] http://www.ambercite.com/amberblog/tags/tag/foundation-patents.html