Detailed background on rqlite can be found on these blog posts. Note that master represents 2.0 development (which is still in progress), with a new API and Raft consensus module. If you want to work with 1.0 rqlite, you can find it here.
rqlite is a distributed system that provides a replicated SQLite database. rqlite is written in Go and uses Raft to achieve consensus across all the instances of the SQLite databases. rqlite ensures that every change made to the database is made to a quorum of SQLite files, or none at all.
rqlite gives you the functionality of a fault-tolerant, replicated relational database, but with very easy installation, deployment, and operation.