A time-driven trigger is a function that executes either at a specific time or at a given time interval. An example of a case where you might use a time-driven trigger is if you have a function that pulls data from a Spreadsheet into a report and emails it to some of your contacts on a weekly basis. See Using Time-Driven Triggers for more details about how to set up these triggers.
Permissions and Time-Driven Triggers
Time-driven triggers are private. To install a trigger, the active user must have at
least read permissions for the script; in other words, the user must be
able to open the script in the Script Editor. Triggers cannot be shared,
regardless of whether a script is shared.
When a script is triggered, it executes under the identity of the owner of the trigger (the person who installed the trigger), rather than the active user.