What does Acts 9:10 mean?

Although it was rarely under Jewish control, Damascus was an important city at this time. It is located about 133 miles north and a little east of Jerusalem, right at the crossroads of the trading routes from the east, down through Israel, and on into Egypt.

Ananias is a common name in the book of Acts. This Ananias is neither the husband of Sapphira (Acts 5:1–6) nor the future high priest (Acts 23:2; 24:1). Nor is he the Aeneas who is healed from paralysis (Acts 9:32–34). Later, Saul will describe him as "a devout man according to the law, well-spoken of by all the Jews who lived [in Damascus]" (Acts 22:12).

The man is called "devout" and has a positive reputation among the Jews. He's likely a Gentile who worships the Jewish God. If so, it's appropriate that God calls him to lead the future "apostle to the Gentiles" to Christ.

God contacts Ananias in a "vision," meaning a prophetic experience while he's awake. This is different from a dream, which happens when the person is sleeping. Several people in the New Testament had visions, but since the compilation of the New Testament, they have become much rarer. Today, it seems God sends visions to those who are looking for Him but do not have access to the Bible—this has been mentioned in some Muslims' testimony of their conversion to Christianity.