Salesforce Apex Trigger Events – Biswajeet Samal's Blog

Before Insert: Trigger that executes due to an insert operation and before the record is saved to the database it is a before Insert trigger
Before Update: Trigger that executes due to an update operation and before the record is saved to the database it is a before update trigger
Before Delete: Trigger that executes due to a delete operation and before the record is saved to the database it is a before delete trigger
After Insert: Trigger that executes due to an insert operation but after the record is saved to the database it is an after Insert trigger
After Update: Trigger that executes due to an update operation and after the record is saved to the database it is an after update trigger
After Delete: Trigger that executes due to a delete operation and after the record is deleted from the database it is an after delete trigger
After Undelete: Trigger that executes due to a undelete operation and after the record is undeleted from the database it is an after undelete trigger