“We read in the New Testament about disciples and apostles, and we tend to think that the two words are synonymous. They are not. A disciple is a learner, a student. An apostle is one who is commissioned by his master with the master’s own authority, then sent out in the master’s name. That distinction is critically important for us because the New Testament tells us that the prophets and the Apostles are the foundation of the church (Ephesians 2:20). That means the apostles had what we call “apostolic authority” over the church of all ages, which authority they were given by the One who sent them.
The first Apostle in the New Testament, the Apostle par excellence, was Jesus. He said, “I have not spoken on My own authority; but the Father who sent ME gave Me a command, what I should say and what I should speak” (John 12:49). Our Lord Himself is the supreme Apostle of the Father, for He carries in His ministry nothing less than the authority of the Father. The twelve, however, were Jesus’ Apostles, having been chosen from the much larger group of disciples who followed Jesus (see Luke 6:13). Thus, Jesus gave to them His own authority.”
Copied from pages 122-123 of R.C. Sproul’s commentary, Mark: He Taught Them As One Who Had Authority.