The word 'apostle' means one who is sent out on a mission. The word 'disciple' means one who is being taught, trained, and disciplined in the ways of his master. Luke 6:13 says, 'And when it was day, He called His disciples to Himself; and from them He chose twelve whom He also named apostles.' Jesus had many disciples who followed Him so that they could learn from Him and be trained by Him. But He named only twelve of them to be apostles. These are the ones He sent out to begin the New Testament Church.