“[Apollos] was acquainted only with the baptism of John. He began to speak boldly in the synagogue, and when Priscilla and Aquila heard him, they took him into their company and explained the way of God more accurately to him.”
~Acts 18:25,26

Apollos was an eloquent Jew of the well-educated city of Alexandria. (Acts 18:24)
He evidently learned of Jesus at least nineteen years prior to this account, before Pentecost and the pouring of holy spirit.
Despite being well-versed and a skilled speaker, he humbly allowed the Christian couple to spiritually enlighten him.
In time, he came to be a respected missionary working under the congregation’s arrangements. (Titus 3:13)
In our ministry, we sometimes encounter spiritual people who are somewhat familiar with the Scriptures and who profess faith in Jesus.
If we patiently help them develop a more accurate knowledge, we may be surprised at their willingness to learn the truth and serve God alongside us. (1 Cor. 3:6,9; 1 Tim. 2:3,4)