What is the difference between Trigger and Workflow in salesforce?

Hi Suraj

Below are  some points that helps you in differentiating between workflow and trigger

Workflow

• You cannot create records
  They currently can only result in a task, email, field update, or outbound message
  They can only cross objects in a master detail relationship, from the detail to the master, and only for certain scenarios (all custom to custom objects, some custom to standard objects, and even fewer standard to standard)
• We can not perform Dml operation in workflow
• We cannot query from database

Trigger

• Can do these things, but obviously using code.
  Often needed for roll-up type scenarios where roll up summary fields cannot be used
  Often needed when a record needs to be created on a different object
• We can use 20 Dml operations in trigger
• Trigger can be used to invoke a webserive

Hope this may help you:

Adding some points:

Workflow

Workflow is automated process that fired an action based on Evaluation criteria and rule criteria.

We can access a workflow across the object.

We cannot perform DML operation on workflow

We cannot query from database

Trigger

Trigger is a piece of code that executes before or after a record is inserted or updated.

We can access the trigger across the object and related to that objects

We can use 20 DML operations in one trigger.

We can use 20 SOQL’s from data base in one trigger.

Thanks

Workflow: Workflow is automated process, a point and click which doesn't need any coding. When you want to take action (email, task, field update or outbound message) for the same object or from Child to parent object, you can use Workflow rules. You cannot perform DML operation on workflow. Workflows work only after some actions.

Trigger: Trigger is a programmatic code approach which fires when before or after a record is inserted, updated or deleted. Using trigger you can work on multiple objects. You can query and you can perform any DML operation. The trigger works before and after some actions.