Paul concludes this letter to the Corinthians in his usual manner, that is to say now that the pastoral and theological issues have been addressed here are some personal greetings and intentions. Notice the collection (12:1-4)-- it is generally believed this collection is part of the relief fund for the destitute in Judea. This fund is addressed in more detail in 2 Corinthians and elsewhere. Paul addresses his travel plans and tells the Corinthian church what he is doing and who is working with him.
Finally come greetings and a final word. In 15 and following Paul talks of three Corinthians who have been working along side of him -- Stephanas, Fortunatus and Achaicus and assisting him in his work in Ephasus. Aquila and Prisca (Priscilla) are fellow makers of tents and close companions of Paul. They appear in several letters and the book of acts.
Notice the signature sentence 12:21 "I, Paul, write this greeting with my own hand." Paul generally dictated his letters -- his scribe is not named in this letter but is in other letter (see Romans 16:22).
Verse 22 has a good Aramaic phrase that is translated "Our Lord, come!" the phrase is marana tha! (or maran atha!) It is usually mispronounced in the modern world. Either way it was one way that the early Christian movement exchanged farewells -- by reminding each other that Jesus is coming back -- Our Lord, come!