Although unquestionably an eloquent speaker, Apollos had a major flaw that was not necessarily of his own making. He deficiency was that he only knew about Jesus through the preaching of John the Baptist (see Acts 19).
Aquila and Priscilla decide to help Apollos by giving him more complete information regarding the Messiah. They introduce themselves to him and are soon filling in all his gaps of knowledge in the "way of the Lord."
Apollos, after coming to a much broader understanding of the gospel message, expands his service into Achaia. The brethren in Ephesus even write a recommendation letter encouraging other disciples to accept and listen to what Apollos has to say. Wherever he goes he preaches about the Messiah. His ability to explain and expound the scriptures is such that the Jews cannot counter his arguments that, indeed, Jesus is the Messiah of man.
The apostle Paul ultimately meets Apollos and considers him a fellow preacher of the gospel.
The next few times Apollos is mentioned in the Bible is in the book of 1Corinthians. In 1Corinthians 1 Paul chastises the Corinthian church for their party spirit of aligning themselves behind particular preachers like him, Apollos or Peter (verse 11). He reiterates his point regarding their immature behavior of 'playing favorities' by again mentioning Apollos (1Corinthians 3:4).
Paul, in his closing remarks to the church at Corinth, states that his fellow laborer is not all that eager to revisit them (no doubt due to the party spirit he saw for himself when he visited - see Acts 19:1).
Now, about brother Apollos. I have often encouraged him to visit you with the other believers, but he is not completely convinced that he should go at this time (1Corinthians 16:12).