A Classic Mac screen has a resolution of 72 dpi, which is the standard upon which software is written. Some monitors deviate from 72 dpi, so documents may look larger or smaller that they will print out. Check the application's ruler. A LaserWriter has a resolution of 300 dpi while a Linotronic can go up to 2540 dpi. One of Mac's greatest innovations when it came out in 1984.
Resources are small chunks of program code that can be used over and over by applications.
Every element of the Mac interface which we have come to know and love is a resource. Menus, icons, cursors, keyboard layouts, and many other things are resources. System software is largely composed of resources. A part of an application where the programming instructions specific to that application are stored. The resource fork is composed of separate resource packages, like volumes in an encyclopedia.