There are four different "types" of Apostles written about in scripture.
(1) Jesus Christ was an Apostle. Jesus was a one of a kind Apostle as God gave him the Spirit without "measure".
Heb 3:1 Therefore, holy brothers, you who share in a heavenly calling, consider Jesus, the apostle and high priest of our confession,
Apostle meaning "one who is sent, a messenger". Jesus was sent, and a messenger of God to proclaim the Gospel to men. Jesus operated in all five "ministry" gifts as a Apostle, Prophet, Evangelist, Pastor and teacher.
(2) The second type apostle are the "Apostles of the Lamb". The twelve Apostles are in a class of their own. No one else can ever be a Apostle of the Lamb.
Rev 21:14 And the wall of the city had twelve foundations, and on them were the twelve names of the twelve apostles of the Lamb.
These twelve Apostles were sent for to be eyewitnesses of Jesus life, earthly ministry, and resurrection. Their main purpose was to be ministers of the Gospel. They were the first to preach, and teach the Word of God.
The Apostle Paul would not qualify to be one of these Apostles as he did not follow Jesus from the start to the end of his earthly ministry. There have been around twenty people in the Bible that have been called "Apostles", or "sent ones", but only the original twelve are considered an Apostles of the Lamb. There are only twelve foundations that support the heavenly city, not 13 or 14....ect
(3) The third type of Apostle would be the Apostle Paul, who helped lay the "doctrinal" foundation of the New Testament. Paul wrote about half of the New Testament, and the revelations he taught did not come from man.
Eph 3:1 For this cause I Paul, the prisoner of Jesus Christ for you Gentiles,
Eph 3:2 If ye have heard of the dispensation of the grace of God which is given me to you-ward:
Eph 3:3 How that by revelation he made known unto me the mystery; (as I wrote afore in few words,
Eph 3:4 Whereby, when ye read, ye may understand my knowledge in the mystery of Christ)
Eph 3:5 Which in other ages was not made known unto the sons of men, as it is now revealed unto his holy apostles and prophets by the Spirit;
The Apostle Paul preached the "revelation" of the Gospel to the early Church saints. We do not need to lay any other foundation which is already laid for us, we are only to build upon that foundation!!
Eph 2:19 Now therefore ye are no more strangers and foreigners, but fellowcitizens with the saints, and of the household of God;
Eph 2:20 And are built upon the foundation of the apostles and prophets, Jesus Christ himself being the chief corner stone;
The Apostle Paul tell us this.....
1Co 3:10 According to the grace of God which is given unto me, as a wise masterbuilder, I have laid the foundation, and another buildeth thereon. But let every man take heed how he buildeth thereupon.
There are no NEW revelations being given to the Church as a "foundation". Paul warned the Church that we are to take heed to how we build upon that which has already been laid. Even though there are no new revelations as foundations to the Church, but there are new revelations about this foundation which we have already been given.
(4) The fourth type of Apostle is the what we have today in the Church. They are sent ones, and their apostleship is in a measure unlike other foundational apostles like the original twelve, and the apostle Paul who laid the very foundation of the Gospel. Epaphroditus was called a "messenger" by Paul. The word, "messenger" means "Apostle". Epaphroditus was not an Apostle in the same sense as Paul or the other twelve apostles were. He was "sent"out as a delegate, or representative, or as the commissioned representative of a congregation.
Today's Apostles are commissioned by the Holy Spirit to bring a specific message or ministry along a certain scriptural lines to the Body of Christ. These modern day “apostles” would be known as “missionaries” They simply build upon the foundation that has already been laid.
One of the most notable signs of a Apostle is their anointing to teach, and preach the Word of God, and to start or plant new Churches.