Mark was not an apostle, but according to the Acts of the Apostles, he accompanied St. Paul and Barnabas on Paul's first missionary journey, but deserted and returned to Jerusalem. He was a close associate of Paul. Matthew was one of the 12 apostles, some do not mention him directly as Matthew but call him Levi... Catechism of the New Testament, with P. Flavien Andriamirijanirina.