If grep is one of your favorite tools, chances are that you will like ack even better. ask a Perl-based command-line utility similar to grep, but designed to improve the search speed and capabilities of grep. Especially if you are a programmer, I strongly recommend replacing grep with ack.
The xargs command is extremely useful when we combine it with other commands. This tutorials explains the usage of xargs command using few simple examples. These example will help you understand the basics of how xargs command works.
Chaining of Linux commands means, combining several commands and make them execute based upon the behaviour of operator used in between them. Chaining of commands in Linux, is something like you are writing short shell scripts at the shell itself, and executing them from the terminal directly. Chaining makes it possible to automate the process.