Workflow Rules:

• Workflow is an automated process that fired after an action, based on evaluation criteria and rule criteria.
• Workflow actions are Field Update, Email alert, Task alert and outbound message.
• Workflow will be helpful to update the same object or master object in custom master-detail relationships.
• We cannot fire workflows after record has been deleted.
• We cannot query from database on workflow.

Trigger:

• Trigger is a piece of code that executes before or after, when an DML event occurs like insert, update or Delete.
• Trigger executes before or after these types of operations insert, update, delete, merge, upsert & undelete.
• We can access the trigger across the object and related to that objects.
• We can use DML operations in one trigger.
• We can use SOQL’s from data base in one trigger.