Navigating files and folders
Each time you open Terminal, you begin in your Home folder. To confirm this, type pwd and press Enter. The command pwd tells you where you are (i.e. your “Present Working Directory”). Any commands you type there will by default occur in this folder (unless you refer to some other directory explicitly.)
After opening Terminal and typing pwd on my computer, it returned /Users/richard.
To navigate to a new folder, use the cd (”change directory”) command. For example, to switch to the Applications folder, type cd /Applications. You can then type ls to list all of your Applications.
To move deeper into the hierarchy, use cd and the name of the folder. For example, if I’m in /Users/richard, I can type cd Movies to move into the Movies folder. I’ll then be in /Users/richard/Movies.
To move back a folder, use two dots (..). For example, if I’m in /Users/richard and type cd .. I will then be in /Users.

October 18th, 2006 at 2:39 pm
A few more notes of interest for navigating files and folders.
To get back your Home directory you can use ‘cd ~’ or just simple ‘cd’ with no specified path will take you back to your Home.
The two dots (..) can also be used to refer to a directory, not just only to go up one directory. For instance if you were in /Users/richard/Movies and wanted to get to /Users/richard/Pictures, instead of using the absolute path you could say ‘cd ../Pictures’.
Also, to make navigating quicker, you can type the first few characters of a directory or file name and press tab, and it will auto complete up to the point where there are several files or directories that start the same way.
For instance, if I type cd /App and hit tab, it will fill out Applications, because nothing else in my root directory begins with App. Since I have Classic mode installed I have a /System for OS X and a /System Folder for OS 9. If I typed ‘cd /Sys’ and pressed tab, it would fill out System. If I actually wanted System Folder, I would have to then type a little more ‘\ F’ (remember the preceding ‘\’ when you have a space in a file or directory name) and hit tab again and it would finish out the whole ‘cd /System\ Folder’
October 23rd, 2006 at 1:50 am
using “cd -” will change the directory to the previous directory where you were (almost like a back button in a browser)