Symbian Ltd. was a software development and licensing company. It was established in 1998 as a partnership between Ericsson, Nokia, Motorola, and Psion. It was acquired by Nokia in 2008.
Symbian OS is a mobile operating system designed for smartphones. It is the continuation of Psion's EPOC as Release 6 of EPOC was simply renamed Symbian OS, though the version number was kept so it was Symbian OS 6.0.
The last release was Symbian OS 10.1 in 2011, which was renamed first Symbian Belle, then Nokia Belle. Nokia Belle Feature Pack 2 in October 2012 seems to have been the last update to the OS.
The last Symbian-powered smartphone is the Nokia808 Pureview in 2012. Symbian OS is now maintained by Accenture.