Difference between getTestBed and TestBed

Lets say i have a test config like below

 TestBed.configureTestingModule({
            imports: [HttpClientTestingModule],
            providers: [SomeService]
        });

        injector = getTestBed()

If i want to get the inject service , what’s the difference between the

TestBed.get(SomeService)
injector.get(SomeService)

Source: New feed
Source Url Difference between getTestBed and TestBed