Initial teaching certificates have different names in different states. Some states, like Michigan, offer an emergency teaching certificate in order to fill a specific need in a classroom that can't be filled by a certified teacher. Usually these expire at the end of the school year and may or may not be renewed depending on the situation. Emergency certificates are usually issued to substitute teachers or specialists in a critical field such as speech pathology, foreign languages, math or science.
Probationary certificates are issued to fully certified teachers within the state that are new at teaching. These expire after a few years or more and can be renewed when the applicant fulfills certain requirements such as taking additional classes or meeting minimum years of work experience. Renewed probationary certificates don't always lead to permanent ones.
Professional certificates, sometimes called Continuing Certificates, are awarded to teachers with advanced degrees and many years of full time teaching. Only well-seasoned veterans are granted these licenses and most states also require the holders of these certificates to still take additional courses or training.
A wide range of endorsements to teaching certificates can be added such as education in additional subject areas, special education eligibility or even administrative options. These are usually added after teachers take additional courses in the area which they are interested in specializing.
Although there now exists a national accreditation for K-12 teachers that is accepted across the U.S., many states still ask applicants to take orientation courses in areas like local curriculum and assessment programs. Some states have mutual agreements with one another and teachers can be certified in one yet work in both. However, passing the national accreditation requirements are quite challenging and highly respected. Some teachers work to get a national certificate even though their jobs don't require it just for the prestige involved.