General
All three synoptic gospels capture that Jesus casts out demons in a non-Jewish region across the sea southeast of Galilee. This account features the strongest demons on record, and it serves to demonstrate how the Lord can set us free from many harmful things and order our lives. Mark and Luke differ from Matthew mainly in focusing on one man who wished to join the disciples following Jesus during His earthly ministry.
Gadarenes, Gergesenes, Gerasenes
There are variations in the ancient copies of the gospels on the name of the place in this episode. Some copies call the place Gadara, others Gergesa, and still others Gerasa. Unfortuntely, many scholars see the variation as a challenge to the idea we have the original text—or even worse, as a denial of the divine inspiration of Scripture!
The truth is far simpler. All three places are southeast of the Sea of Galilee, opposite Galilee. From the perspective of Matthew's Jewish audience, these were all basically the same: over that way, on the other side of the sea.
None of the named places pose a problem for the text, either. Gadara and Gergesa in particular are mountainous and near the sea, perfectly suited to this account. Gerasa is several miles away from the seashore, but this, too, is no problem; nothing in the account requires the people of the town to have come out within the space of hours or even on the same day.