^^ This.I’d recommend reading the section in the Catechism on the Church as “apostolic”:
CCC 857–865
As Deacon Jeff said the bishops are the successors to the apostles, but “apostles” in the strictest sense were those chosen witnesses of Jesus’ Resurrection and thus we don’t call bishops “apostles” in the same way.
But, there is a sense in which we all participate in the apostolic mission of the Church (i.e. being sent out to take the Gospel to the world around us).
The regular definition of “apostle” is one who is sent, but those deemed the holders of the Apostolic office, or the Apostles are those who meet the eyewitness criteria, and received their Holy Orders from Christ.
This means the original 12, to which Mathias was admitted to replace Judas, and St. Paul. Barnabas is also deemed Apostle in the liturgy of the Roman Rite, but this may be due to his heavy missionary activity alongside St. Paul, and his day is a Memorial rather than the more usual Feast.
When it comes to the Office itself, for the purposes of Apostolic succession and the determination of divine revelation, we limit the definition to these men, from which the Apostolic succession gets its source. We have a rather specific axiom: “Public revelation closed with the death of the last Apostle.” This means, with the death of St. John, there is no more additional divine revelation. So it’s specific. We are all disciples (followers), and we are called to be apostles (“sent”), but the time of the Apostles has long since closed.