When we use plugins in MS Dynamics CRM, sometimes we may need to use more than one plugins with common trigger event. In order to handle this scenario, we have a property in Plugin Registration tool. Its called 'Execution Order'. So the plugins which share same trigger event could be assigned with a Execution order. Execution Order numbering starts from one. Even if all the plugins share the common trigger event, the Plugin with Execution order 1 would be executed first and then the rest. Hence we could decide this order according to our requirement.
Imagine that we have two plugins
1.Plugin : AssignOwner
2.Plugin : Calc
Both of these must be fired when we create a contact and also as Pre-Operational.
But as per our requirement we decide that Plugin 'Assign Owner' should be executed first and then 'Calc'
So it could be done while defining the step.