As you see a template consists of several files, each file is used for a certain part of the template. Some files are used for multiple pages. The developers of phpBB have been quite ingenious in using the same files for several different functions to keep the number of files to a minimum.

The page below has a list of all the files and explains the function of each of them, I suggest you read it and familiarize yourself with it. Make sure to add it to your bookmarks/favorites for quick access later, it will come in handy as you proceed.

http://www.jakob-persson.com/node/542

All the files for the Administration Panel area are located in the admin/ folder in your myTemplate/ folder, you will not have to edit these files as they are only visible to the administrator of the board. I use subSilver default files for this area, it saves me time not having to update these files manually every time changes are made to the phpBB template files.