Fast Switching To Previous Directory In Linux Terminal

I had a scenario in which I had to switch between two directories frequently while I was working on the remote server over SSh. Typing the directory paths frequently was getting so tedious that I had to know some way to switch between two directories with a single short command. Here is a small tip that will be useful in such cases.

I am presenting my scenario and you'll be able to adapt with your own scenario. So following are two directories I keep on working always.

/opt/lampp/htdocs/
and
~/gateway/bandMan/

So I have the scenario something like below.

cd /opt/lampp/htdocs/

I cd to the first directory with the command above and then perform series of numerous commands and then suddenly I've to go back to the second directory. And I do so by following command:

cd ~/gateway/bandMan/

Again, after changing the directory, I perform several commands and after finishing my tasks on this folder, I need to switch back to previous directory. And I type the following command:

cd -

How it works
This information is for the tech enthusiasts who like to know how it works. When I navigate to another directory from the shell for the first time, a new environment variable OLDPWD is set which stores the path for previous directory before the last cd command was executed. Now what cd - does is switch to the path that OLDPWD variable is storing. If OLDPWD is empty, you will see the "bash: cd: OLDPWD not set" error.

Isn't it so simple? I hope you like this small tip. :)