Terminal lets you see all of the files (including hidden ones, if you search appropriately).
You can get to some of the other files and folders using the "Go to Folder..." command (shift-⌘-G) in Finder and heading for places like "/usr".
However, going to places Finder doesn't normally let you go can cause you to mess up files essential to the proper running of OS X, so I wouldn't do it lightly.