GED is an abbreviation for General Educational Development. It is the name of a test. If you pass the test, you receive a high school diploma.
GED does not stand for General Education Diploma. It is not a degree of any kind. Let me state it again: GED is the name of the test.
While people might call the degree earned with a GED an “equivalency diploma” or some other such nonsense, there is virtually no difference between it and a run-of-the-mill high school diploma.
If you pass the GED, you get a high school diploma. Don't call it anything else. And whatever you do, don't say someone "got his GED." Please.