NVRAM
Non-volatile Random Access Memory is a special type of RAM that is not cleared when the router is rebooted.
The startup configuration file for the router is stored in NVRAM by default.
When the router is first shipped, the configuration file is not present.
NVRAM stores all the user-defined configuration information for the router, which includes the host name of the router, the routing tables, and the protocol configurations.
The configuration file is the first file that the person who sets up the router creates. This configuration file, like the IOS in flash memory, is typically backed up on a TFTP server.