What exactly is NoSQL?

Question

What exactly is NoSQL? Is it database systems that only work with {key:value} pairs?

As far as I know MemCache is one of such database systems, am I rig

Answer 1

Take a look at these:

http://en.wikipedia.org/wiki/Nosql#List_of_NoSQL_open_source_projects

and this:

http://www.mongodb.org/display/DOCS/Comparing+Mongo+DB+and+Couch+DB