During a vi session, you can mark your place in the file with an invisible "bookmark," perform edits elsewhere, then return to your marked place. In command mode:
mx'x(apostrophe) Moves the cursor to the first character of the line marked by x.
`x``(backquotes) Returns to the exact position of the previous mark or context after a move.
''(apostrophes) Returns to the beginning of the line of the previous mark or context.
NOTE: Place markers are set only during the current vi session; they are not stored in the file.