Term probably popularized by Philip Greenspun.
It is a particular type of website anyone can inexpensively build using:
All it cost is your time and effort (which is not free), an inexpensive but durable PC, and Free Software.
To make everything work together you'll have to fulfill a few responsibilities:
To kick off your learning experience (so you too can run a database-backed website like the big boys) try Philip Greenspun's book: Philip and Alex's Guide to Web Publishing.