Priority is defined as the order in which the defects should be resolved. The priority status is usually set by the testing team while raising the defect against the dev team mentioning the timeframe to fix the defect. The Priority status is set based on end users requirement.
For example: If the company logo is incorrectly placed in the company's web page then the priority is high but it is of low severity.
Priority can be marked as either of the following states:
Low - This defect can be fixed after the critical ones are fixed.
Medium - The defect should be resolved in the subsequent builds.
High - The defect must be resolved immediately because the defect is affecting the application to a considerable extent and the relevant modules cannot be used until it's fixed.
Urgent - The defect must be resolved immediately because the defect is affecting the application or the product severely and the product cannot be used until it has been fixed.