JOEL - Here are the scriptures in question:

1. AND in those days, when the number of the disciples was multiplied, there arose a murmuring of the Grecians against the Hebrews, because their widows were neglected in the daily ministration.
2. Then the twelve called the multitude of the disciples [unto them], and said, It is not reason that we should leave the word of God, and serve tables.
3. Wherefore, brethren, look ye out among you seven men of honest report, full of the Holy Ghost and wisdom, whom we may appoint over this business.
4. But we will give ourselves continually to prayer, and to the ministry of the word.
5. And the saying pleased the whole multitude: and they chose Stephen, a man full of faith and of the Holy Ghost, and Philip, and Prochorus, and Nicanor, and Timon, and Parmenas, and Nicolas a proselyte of Antioch:
6. Whom they set before the apostles: and when they had prayed, they laid [their] hands on them.
7. And the word of God increased; and the number of the disciples multiplied in Jerusalem greatly; and a great company of the priests were obedient to the faith. (Acts 6:1-7)

The foreign or Hellenistic Jews in Jerusalem were complaining that their widows were being neglected and not taken care of like the widows of the native Jews. The Twelve told the meeting that it was not reasonable for them to leave their important office of teaching the gospel to provide for the daily welfare of the widows and serve their tables. There were other good men(disciples) who could look after these duties so the Twelve could continue to devote themselves to the charge of teaching the gospel to all people. So the seven that were chosen(including Stephen) were not considered Apostles, but they were chosen and ordained by the Twelve to take the lead in ministering to the widows and other administrative duties.
There is an interesting modern parallel to this. In December 1978, the First Presidency and Quorum of the Twelve made a similar determination that it was no longer advisable for the Twelve to occupy their time in the details of administration of the many Church departments. They delegated seven men, designated as the presidents of the First Quorum of the Seventy, to give supervision to these details so that the Twelve could devote their full energies to the overall direction of the work, and, as directed by the Doctrine and Covenants.