Router components and their functions:

Components CPU Executes operating system instructions
RAM Contains the running copy of configuration file. Stores routing table
ROM Holds diagnostic software used when router is powered up.
NVRAM Store startup configuration. This may include IP address (Router protocol, Hostname of router)
Flash memory Contains the operating system (Cisco IOS)
Interface There exist multiple physical interfaces that are use to connect network.
Examples of interface types:
     - Ethernet/FastEthernet interfaces
     - Serial interfaces
     - Management interface