Move cursor to first (highest) line in current window.
Move cursor to the lowest line in current window.
Move cursor to the middle of the current window.
vim +2 file.txt
Insert the file file.txt below the cursor in current buffer.
:r file.txt
Insert the file file.txt before the first line.
:0r file.txt
Insert lines 2 to 8 from file file.txt below the cursor.
:r!sed -n 2,8p file.txt
Insert a directory listing below the cursor
:r !ls