Triger.new is a command which returns the list of records that have been added recently to the sObjects. To be more precise, those records will be returned which are yet to be saved to the database. Note that this sObject list is only available in insert and update triggers, and the records can only be modified in before triggers.
But just for your information, Trigger.old returns a list of the old versions of the sObject records. Note that this sObject list is only available in update and delete triggers.
