1. Linux: Absolute Path
$ cd /usr/lib$ cd /usr/lib pwd
See this path (linux#1/usr/lib), when you give PWD, it gives a full path from the root level. This is called absolute or full path.
Think of the absolute pathname as being the complete mailing address for a package that the postal service will deliver to your next-door neighbor.
2. Linux: Relative Path
$ cd usr$ /user cd lib
$ /usr/lib pwd
$ linux#1/usr/lib ==> Going step by step and achieving.
$ linux#1/usr/lib cd ../../ ==> This is the method of going back step by step.
$ linux#1 ==> This is root level directory
You are currently in the lib directory. So relative path nothing but complete information of all the mother directories.
Here, for lib, the usr is the mother directory.
In simple terms, it is a step-by-step way and to reach your target directory.
You might aware the .. (double dots), means you'll go to the mother of the current directory.
Think of the relative directory name as giving the postal carrier directions from your house to the one next door so that the carrier can deliver the package.
3. How to go back to the home directory
You currently in the 'lib' directory.
$ cd
$ linux#1 ==> This is your home directory.
If you type cd, without any arguments, it will go to the home directory.