Jesus went all over Galilee teaching in the [Jewish] synagogues and preaching the good news of the [coming, see verse 17] kingdom, and healing all kinds of disease and sickness among the people.
This message was about Jesus from Nazareth and how God specially chose Him [and signified it] by giving Him the Holy Spirit and power. He traveled all over doing good [for people] and healing everyone who was [being] oppressed by the devil, for God was with Him.
Preach the [Gospel] message; be prepared [to do it both] when it is convenient and when it is inconvenient; reprove [i.e., convince people of their wrongdoing], rebuke [i.e., convict people of their sin], and exhort [i.e., urge people to act], with great patience and teaching.