* Certification often refers to the *process* of meeting the requirements (education, testing, etc.) to become eligible for a license. You *earn* certification, which then *qualifies* you for a license.
* License is the *actual document* or official record that grants you permission to teach. It's the tangible outcome of successful certification. You *receive* a license after completing the certification process.
Think of it like a driver's license: You go through the process of driver's *certification* (passing the written and driving tests), and then you *receive* your driver's *license*.
In short, the distinction is often blurred, but certification is the process, and the license is the result. The specific terminology may vary slightly by state or country.