The terms Priority and Severity are used in Bug Tracking to share the importance of a bug among the team and to fix it.

Severity

1. The Severity status is used to explain how badly the deviation is affecting the build.

2. The severity type is defined by the tester based on the written test cases and functionality.
Ex : If an application or a web page crashes when a remote link is clicked, in this case clicking the remote link by an user is rare but the impact of application crashing is severe, so the severity is high and priority is low.

Priority

1. The Priority status is set by the tester to the developer mentioning the time frame to fix a defect. If High priority is mentioned then the developer has to fix it at the earliest.

2. The priority status is set based on the customer requirements.
Ex : If the company name is misspelled in the home page of a website, then the priority is high and the severity is low to fix it.