Question

Sorry if this question is somewhat subjective. I am new to ‘could store’, ‘distributed store’ or some concepts like this. I really wonder what do they have in common and want to get an overview on all of them. What do I need to prepare if I want to write a product similar to this?

Answer 1

The NoSQL Database site summarizes the concept like this:

Next Generation Databases mostly
address some of the points: being
non-relational, distributed,
open-source and horizontal scalable.
The original intention has been modern
web-scale databases. The movement
began early 2009 and is growing
rapidly. Often more characteristics
apply as: schema-free, replication
support, easy API, eventually
consistency, and more. So the
misleading term “nosql” (the community
now translates it mostly with “not
only sql”) should be seen as an alias
to something like the definition
above.

That site also maintains an archive of articles on NoSQL databases. Most of them seem to focus on particular products but there are some more general overviews. If you are serious about building your own one then Design Patterns for Distributed Non-Relational Databases does a good round up of things you need to consider.