What is Database.com in salesforce?

Database.com is built from the ground up to power a new generation of enterprise applications that are cloud, mobile and social
Database.com is open – for use with any language, platform and device
Database.com enables developers to focus on building great apps, instead of managing and maintaining databases and hardware
Database.com leverages the infrastructure and technology trusted and proven by more than 87,000 salesforce.com customers over 11 years – now a standalone cloud database