Hello @Sri,
TestNG is a Testing framework, that covers different types of test designs like a unit test, functional test, end to end test, UI test and integration test.
You can run a single or multiple test cases in your Testng code.
If test priority is not defined while, running multiple test cases, TestNG assigns all @Test a priority as zero(0).
Now, while running; lower priorities will be scheduled first.
Different types of TestNG code Priority are:
TestNG code without Priority
TestNG code without Priority in Alphabetical Order
Set Priority in TestNG
Methods with Same Priority
Combining both prioritized(having same priority) and non-prioritized methods
However, if you want to know more about how this Different types of TestNG code Priority works with example you can refer this:TestNG code Priority
Hope it helps you!!
Thank you!!