There are many different teaching certifications out there for aspiring English teachers. The most common ones are TEFL, TESOL, TESL, and CELTA.
While many countries will accept a TEFL, TESOL, or CELTA certification, it is important to note that some countries (and schools) may only accept a specific certification. It is common for schools in China and in some European countries to only accept teachers with a CELTA degree. Make sure you research the schools in the country you would like to teach in before getting you certification so you have the proper one.