I am trying to study the meaning of apostolos in 1 Corinthians, and in some sense, it seems to mean an official ambassador sent out on a mission from a higher, unquestioned authority. Jesus was also called an apostolos sent from God in Hebrews. My confusion comes from 2 Crinthians 5, where Paul says we are all "ambassadors," but Paul uses a different term, the word presbeuo. In 1 Corinthians 12:29, however, it makes it clear that not everyone is an apostolos. Here's my question: I am confused about the difference in meaning between apostolos and presbeuo. Is there a difference in degree or ranking, in the sense that an apostolos is directly sent by the higher authority, like a senior ambassador or official, and the presbeuo is a junior ambassador? Many thanks.

Many different Greek words can describe Paul's ministry. Let me try to simplify.

An apostle is one sent by another. In its special sense, it's a witness of the resurrected Jesus who is inspired by God to declare his word. See 1 Cor 9:1; Acts 1:22.

An ambassador may or may not be sent. The key thing is that he or she represents another. The concept is similar to being an envoy, or missionary, or however you want to translate apostolos. But it's not the same.