What does Mark 5:11 mean?

Jesus and His disciples are on the shore of the hill country on the east side of the Sea of Galilee. They are near the town of Gergesa which is in the region of Decapolis. Decapolis was a group of ten cities to the east and southeast of the Sea of Galilee, all but one on the east side of the Jordan River. At that time, the area west of the Sea of Galilee was known as Galilee and was home to much of the Jewish population. South of Nazareth was Samaria, home to many different ethnicities, but particularly the descendants of the Jews from the Northern Kingdom of Israel who intermarried with the foreigners their Assyrian conquerors settled in the area. Below Samaria was Judea, where the bulk of the Jews lived.

All of this land was controlled by the Roman Empire, and Decapolis, in particular, was inhabited by Gentiles. So, although it may feel jarring to learn about a herd of pigs in a Bible passage, they are neither banned nor out of place in this region. And they are very practical for the rough terrain. They can forage for their own food, they aren't as foolish as sheep, and they can swim. As with the sheep that are more commonly mentioned in the Bible, their herders are probably not their owners. The herders would be sons or hired hands who work for the owners who may very well live in a city or town.

While God had given Jews strict laws against eating pork (Leviticus 11:7), Gentiles had no such laws. In just a few short years from this story, God will reveal to Peter that even the Jews' restriction against eating pork will be removed, as such laws are fulfilled under the grace of Christ (Acts 11:1–10; 15:1–29; Mark 7:19).