The Home, End, PgUp and PgDn keys allow you a coarse means of moving through a buffer, however, if you want to be in the middle of a thousand line buffer they are very awkward to use. If you go to the command line and type in the number of the line you want to go to (followed by a carriage return to execute) the editor takes this as a command to move your cursor to that line. This gives you the ability to move through the file in absolute terms. For example, if a compiler issues an error for line 458 of a source file then upon reading that source file with the editor you can go right to that line.