Apache CouchDB being a schema-free, distributed, fault-tolerant and document-oriented database accessible via a RESTful HTTP/JSON API.

It is highly robust, incremental replication with bi-directional conflict detection and resolution, and is queryable and indexable using a table-oriented view engine with JavaScript acting as the default view definition language.

CouchDB is written in Erlang, but can be easily accessed from any environment that provides means to make HTTP requests. There are a multitude of third-party client libraries that make this even easier for a variety of programming languages and environments.

CouchDB is not at all a replacement for relational database management system. Instead of storing data in rows and columns, the database manages a collection of JSON documents (early versions of CouchDB used XML).

A CouchDB document is an object that consists of named fields. Field values may be strings, numbers, dates, or even ordered lists and associative maps. An example of a document would be a blog post:

In the above example document, Name is a field that contains a single string value “Kiran Hota”. Tags is a field containing the list of values “plankton”, “baseball”, and “decisions”.

A CouchDB database is a flat collection of these documents. Each document is identified by a unique ID.