nano is a simple text-mode editor - although there are "nicer" gui-editors around - using nano has it's advantages:
Where you replace <file-name> with the local filename or a relative/absolute file-path.
If <file-name> does not exist, it will be created on leaving nano
Use the cursor keys and PgUp PgDn to navigate through the file.
Important functions are listed at the bottom part with the according hotkeys:
^X denotes press CTRL+x (= eXit nano) M-/ denotes press ALT+/ (go to last line) for example.
^G will show the general help and does list all available hotkeys
|nano ~/.bashrc||edit the bash-resource file in the current users home-directory (aka ~)|
|nano ~/.profile||edit the users .profile -file - used to 'export' session-global environment variables|
|sudo nano /etc/default/grub||edit the main input/config-file for grub-menu as root|
|IRC:grubedit.htm||edit kernel params on boot, common use-cases|