Most people must use a passport to travel overseas and reenter their country. A passport is an internationally recognized travel document that verifies your identity and citizenship.
Most foreign countries require a valid passport to enter and leave Ethiopia. Some other countries may allow you to enter with only some kind of other legal document like a birth certificate, or with a birth certificate and a driver’s license. This however differs from country to country. So, please check what you need to have before departing for your destination country and what the requirements of that country are.