Matthew 28:19-20 contains what has come to be called the Great Commission: “Therefore go and make disciples of all nations, baptizing them in the name of the Father and of the Son and of the Holy Spirit, and teaching them to obey everything I have commanded you. And surely I am with you always, to the very end of the age.” Jesus gave this command to the apostles shortly before He ascended into heaven, and it essentially outlines what Jesus expected the apostles, and those who followed them, to do in His absence.
It is interesting that in the original Greek, the only specific command in Matthew 28:19-20 is “make disciples.” The Great Commission instructs us to make disciples while we are going throughout the world and while we are going about our daily activities. How are we to make disciples? By baptizing them and teaching them all that Jesus commanded. “Make disciples” is the command of the Great Commission. “As you are going,” “baptizing,” and “teaching” are the means by which we fulfill the command to “make disciples.”
Many understand Acts 1:8 as part of the Great Commission as well, “But you will receive power when the Holy Spirit comes on you; and you will be my witnesses in Jerusalem, and in all Judea and Samaria, and to the ends of the earth.” The Great Commission is enabled by the power of the Holy Spirit. We are to be Christ's witnesses, fulfilling the Great Commission in our cities (Jerusalem), in our states and countries (Judea and Samaria), and anywhere else God sends us (to the ends of the earth).