From here:
Almost all that we know about Luke comes from the New Testament. He was a physician (Col 4:14), a companion of Paul on some of his missionary journeys (Acts 16:10ff; 20:5ff; 27-28). Material found in his Gospel and not elsewhere includes much of the account of Our Lord’s birth and infancy and boyhood, some of the most moving parables, such as that of the Good Samaritan and that of the Prodigal Son, and three of the sayings of Christ on the Cross: “Father, forgive them,” “Thou shalt be with me in Paradise,” and “Father, into thy hands I commend my spirit.”
In Luke’s account of the Gospel, we find an emphasis on the human love of Christ, on His compassion for sinners and for suffering and unhappy persons, for outcasts such as the Samaritans, tax collectors, lepers, shepherds (not a respected profession), and for the poor. The role of women in Christ’s ministry is more emphasized in Luke than in the other Gospel writings.
In the book of Acts, we find the early Christian community poised from the start to carry out its commission, confident and aware of Divine guidance. We see how the early Christians at first preached only to Jews, then to Samaritans (a borderline case), then to outright Gentiles like Cornelius, and finally explicitly recognized that Gentiles and Jews are called on equal terms to the service and fellowship of Christ.