Difference between BVT and BAT?

As soon as the build recieved..

First one will be Navigation testing. To make sure that there is no broken links or tabs that should not stop from testing.

Second will be Build Verification Test (BVT), 10 to 15% of the total test cases will be executed in this test to make sure the build is stable enough to go for further testing.
eg: If we are not able to add something, both modify and delete cannot be tested.
Then the test will fail.

If BVT fails, the build will be rejected.

Third will be the Build Acceptance Testing (BAT), This can also be called as system testing. Remaining 80 to 85% of the test cases will be executed in this test. That will cover the functionality/ UI etc..