Save - To write (save) the contents of an open (and working) document in the application (from main memory) to a file on the current disk drive, with the same name as the opened document.
Open: To open (read the contents of) a closed document file from a current disk drive, into the main memory (into the application software window), for viewing or editing purposes.
Save => From application (main memory) to Disk drive.
open => from disk drive => application in main memory
New : It is the option to open a blank new document/spreadsheet/presentation in a new window or the current window. The new document is only in the application (main memory) until it is saved.
Open: It is the option to open (read the contents of) an existing document on a disk drive.
New => fresh blank document in main memory (application)
Open => from disk drive into an application main memory