You can set notifications to find out when other people have modified your spreadsheets, and learn what they've modified. You can also choose how often you'd like to be notified i.e. as soon as a change is made, or to receive a summary of changes each day.
To set notifications in a sheet:
Click on the Tools menu and choose Notification Rules
Choose what you want to be notified of i.e. any changes, or form data being submitted into a sheet
Choose how often you wish to be notified
Click on Save