Bash - how do you make it so that the result of a command gets placed into a variable?

For instance, let's say I wish to type the command pwd.

It gives me a really long path to the current directory I am in.

What I would really like to do is make it so that I can go into a completely different directory and still refer to the previous directory I was in, without having to memorize the previous path.

Is there any way to do this?