Levi was a tax-collector. Tax collectors were considered by the Jews to be traitors because they collected taxes for the enemy, the Romans, and exploited their position to their own benefit. They were not allowed in the synagogue, being regarded by the Pharisees as unclean and sinners.
In this bible passage, Levi is rescued by Jesus. He had a sickness like us all, called sinfulness, that only Jesus can heal. Jesus said to him ‘follow me’ and Levi became one of Jesus’ disciples. He took a new name, Matthew, and wrote the gospel of Matthew in the Bible.