Order Of Execution for Triggers :

Old record loaded from  database (or initialized for new inserts)

•                     New record values overwrite old values

•                     System Validation Rules

•                     All Apex "before" triggers

•                     Custom Validation Rules 

•                     Record saved to database (but not committed) 

•                     Record reloaded from database

•                     All Apex "after"triggers

•                     Assignment rules

•                     Auto-response rules

•                     Workflow rules

•                     Escalation rules

•                     Parent Rollup Summary Formula value updated (if present)

•                     Database commit

•                     Post-commit logic (sending email)