Severity: It is the extent to which the defect can affect the software. In other words it defines the impact that a given defect has on the system. Priority: Priority defines the order in which we should resolve a defect. Should we fix it now, or can it wait? This priority status is set by the tester to the developer mentioning the time frame to fix the defect. If high priority is mentioned then the developer has to fix it at the earliest. The priority status is set based on the customer requirements.