There are three modes:

• User EXEC mode: Basic monitoring – Prompt looks like: Switch>
• Privileged EXEC mode: Access to other router commands – Prompt looks like: Switch#
• Global configuration mode: Commands that affect the entire system – Prompt looks like: Switch (config)#

Router>enable (Allows access from user EXEC to privileged EXEC mode)
 
Router#disable (Reverts to user EXEC from privileged EXEC mode)
 
Router#configure terminal (Changes to global configuration mode from privileged mode)
 
Router(config)#exit (Exits from any configuration mode to privileged mode (Ctrl+Z is keyboard shortcut)
 
Router(config)#interface <int>  (Changes to interface configuration mode from global configuration mode, you can configure ports, vlans…)
 
Router(config)#interface <subint> (Enters subinterface configuration mode from global configuration mode)
 
Router(config)#line <line>  (Enters line configuration mode from global configuration mode, configures virtual terminal line)
 
Router(config)#router ospf 2 (Enters router configuration mode from global configuration mode)