Explain Linux / UNIX dot-files

Q. Can you tell me more about dot-files that shell and many UNIX command reads?

A. A dot file is nothing but a configuration file usually stored in users home directory. Dot files are used to configure the settings for many UNIX / Linux programs such as:
=> Bash / csh / ksh shell
=> Vi / Vim and other text editor
=> And many other applications

Usually UNIX like operating system is configured with hundreds of file located at /etc/ or /usr/local/etc or other special directories. Each application has a unique format. User can override many application defaults by creating their own configuration file in home directory. To hide configuration file from normal listing of the home directory, the name of the config file / directory prefixed with a dot (period). Thus, you got name dot file.

You can list dot files using ls command:
$ ls -a $ ls -ld .* $ ls -a | grep '^\.'
Output:

.
..
.adobe
.automatix
.azureus
.bash_history
.bmp
.cache
.config
.DCOPserver_vivek-desktop__0
.DCOPserver_vivek-desktop_:0
.dmrc
.esd_auth
.fontconfig
.fullcircle
.....
......
...
.tvtime
.update-manager-core
.update-notifier
.viminfo
.vimrc
.vlc
.w3m
.Xauthority
.xine
.xsession-errors

You can edit or update all dot files with standard text editor. You can also browse other users configuration file online here.