[addaon]

Branch coverage is also known as decision coverage. Essentially, it means coverage of every machine code instruction in the generated binary. This includes every statement in every 'then' and 'else' (which would be statement coverage), but also includes decisions that are sub-expressions and not statements. Consider:

    if (foo() || bar()) {
      a();
    } else {
      b();
    }

Statement coverage says that a test must cover the lines of code (or statements) `if (foo() || bar())`, `a()`, and `b()`. But if `foo()` is tautological then the || short circuits, and all of your tests can pass, with 100% statement coverage, even if `bar()` causes the sun to go nova. With 100% decision coverage, you must have a test case that causes `foo()` to return false, so that you can test the behavior when `bar()` both returns true and returns false.

Edit: The above isn't a correct example, because statement coverage will not hit `b()` if `foo()` is tautological. Still, you can see the point -- there's a difference between decision coverage and statement coverage.