What does Luke 10:15 mean?

Seventy-two of Jesus' disciples receive His instructions before they scatter into towns and villages. On their journey, they are commissioned to heal, cast out demons, and prepare the people for Jesus' message of God's coming kingdom. If the towns do not accept their message, the disciples are to simply shake the dust off their feet and warn the people that God's kingdom is coming whether they like it or not (Luke 10:1–11, 17). Now, Jesus describes the reception that predominantly Jewish cities are giving to His signs and teaching compared to the theoretical reactions Gentile cities would have given had they witnessed the same evidence.

He begins by comparing the towns that will reject the disciples with Sodom (Luke 10:12). Then He compares Chorazin and Bethsaida, in northeast Galilee, with the Gentile Tyre and Sidon in Phoenicia (Luke 10:13–14). Now, He talks about Capernaum, His base of operations and the home of Andrew, Peter, James, and John.

Matthew combines Luke 10:12 and 15 in a way which more clearly parallels Luke 10:13–14:

And you, Capernaum, will you be exalted to heaven? You will be brought down to Hades. For if the mighty works done in you had been done in Sodom, it would have remained until this day. But I tell you that it will be more tolerable on the day of judgment for the land of Sodom than for you. (Matthew 11:23–24)

Capernaum probably witnessed more healings and other miracles than any other city on earth. And many did repent and choose to follow Jesus. But as a city, they did not; nor did the religious leaders.

"Hades" is a general term for the realm of the dead. Jesus uses it to mean the temporary place where unbelievers will go between their deaths and final judgment. The comparison with heaven and the mention of "judgment" (Luke 10:14) makes it clear that Jesus means a place of torment.