Using the two merging underneath the same roof lately, it is difficult to determine which the main variations between Membase and Couchbase. Why would one be utilized within the other?

I wish to elaborate around the answer distributed by James.

Right now Couchbase server is CouchDB with GeoCouch integration as they are. Things to know about CouchDB is you be capable of create structured documents and do map-reduce queries on individuals documents.

Membase server is memcached with persistence and incredibly simple cluster management interface. It's talents are a chance to do really low latency queries along with the capability to easily add and take away servers from the cluster.

Late this summer time however Membase and CouchDB is going to be merged together to create the following version of Couchbase. What exactly will the brand new version of Couchbase seem like?

At this time in Membase the persistence layer for memcached is implemented with SQLite. Following the merger of those two items CouchDB would be the new persistence layer. What this means is you will get the reduced latency demands and great cluster management which was supplied by Membase and you'll will also get the truly amazing document oriented model that CouchDB is renowned for.

In the Couchbase Product Comparison Table:

Couchbase Server is a fit if:

A single-server solution is enough to support your users and data
Advanced querying and indexing is important
You demand peer-to-peer sync

Membase Server is a fit if:

You have large number of users 
Multiple servers are necessary to support growing user population and data set
Low latency, high throughput are needed for snappy interactive experience