The Samaritans were considered half-Jews and half-Gentiles by the Jewish Community
The Samaritans were a group of people who lived in the territory of the old Northern Kingdom of Israel. This was located north of Jerusalem in the area of Mt. Gerazin and Mt. Ebal. In 722 B.C. the Northern Kingdom of Israel fell to the Assyrian army. Almost all of the population of the Northern Kingdom was deported to various parts of the Assyrian Empire. Many of these the Jewish people of the Northern Kingdom remained. The Assyrian government resettled thousands of people from Assyria into the territory of the Northern Kingdom after it conquered the Jews. After much intermarrying over the years, the territory of the Norther Kingdom was inhabited by half-Jews, and half-Gentiles.
The Samaritans had their own version of the Torah and did not have good relations with those Jews from Jerusalem or other places outside of Samaria. Jesus had an encounter with a woman of Samaria while on His way to Jerusalem. He was thirsty and wanted a drink of water. His disciples had gone into the city to buy supplies. Jesus was sitting by the well of Jacob and a Samaritan woman came by.
And he needed to pass through Samaria. 5 Then He came to a city of Samaria, called Sychar (near the city of Shechem), near the plot of ground that Jacob gave to his son Joseph. 6 Now Jacob’s well was there. Jesus then grew weary on his journey and sat down by the well. It was about the sixth hour. 7 A woman of Samaria came near to draw water. Jesus said to her, “Give me a drink.” 8 For his disciples had gone away into the city to buy food. 9 The the woman said to him, “How is it that you being a Jew, ask me, a Samaritan woman, for a drink of water? For Jews have no dealings with Samaritans. —John 4:4-9
The Samaritans maintained that they were the original descendents of the Patriarchs (Abraham, Isaac, Jacob, and Joseph) and that the Jews of the rest of Israel were not. Presumably because the Southern Kingdom (Jerusalem) was overtaken and destroyed by the Babylonians in 587 with the remaining people being taken as prisoners to Babylon.
History aside, these two groups, the Samaritans and the Jews, did not get along. Around the time of Jesus the Jewish historian Josephus recorded that Samaritans would harass Jews who were traveling thru to attend one of the Feasts of Israel. Samaritans were accused of placing human remains in the area of the Temple in Jerusalem in an effort to desecrate it, while Jews were accused of burning down Samaritan villages in reprisal.
This helps to clarify why the Samaritans were singled out as a group to receive the word of God and then the Holy Spirit baptism in Acts 8. It also serves to better explain some of the history of the relationship between the Jews and Samaritans and a better understanding of the Parable of the Good Samaritan.
As it regards the baptism of the Holy Spirit; these people received it after the Apostle Peter was sent to their region to lay hands on them. He and John laid hands on them and it is recorded in Acts 8 that Simon the sorcerer, who also believed, was able to see that when the Apostles laid hands on the believers they received the Holy Spirit. If Simon was able to see that by the laying on of hands by the Apostles, the Holy Spirit was given, there must have been some visible sign or indication that these believers actually received this baptism. Presumably, it would seem likely from the example in Acts 2:4 that these people began to speak in tongues and/or prophesy, or magnify God.
This serves as one of the four instances in the book of Acts where people received the baptism of the Holy Spirit and began to speak in tongues, prophesy, and/or magnify God. It also serves to identify the group of people who originally received the gift of the Baptism of the Holy Spirit. The Samaritans were Jews of a sort (see Who received the baptism of the Holy Spirit in the book of Acts).