What does the "in good faith" mean?

Of course if as a hobby I want to use their patent to help me build/improve my electric car, then now they won't sue me. But the question is, what if I'm Tesla's competitor, or if I want to be, will they allow me to use their patent when I'm trying to compete with them, and "steal their business"? Because no one will use their patent if they might sue them after for "using their patent against them", but on the other hand, is using their invention against them "good faith"?

Is there no proper and legal way to share their invention that indicates exactly what can and can't be done(something like an open source license)?