When Jesus used a parable, it was always something that his audience would be familiar with. His parables were often about the kingdom of God sometimes called the kingdom of heaven. The word kingdom referred to God's kingly authority over this Earth so Jesus was illustrating how God worked on this planet. Part of God's work is to eventually evaluate every human being.
47 "Again, the kingdom of heaven is like a dragnet cast into the sea, and gathering fish of every kind;
48 and when it was filled, they drew it up on the beach; and they sat down, and gathered the good fish into containers, but the bad they threw away.
49 "So it will be at the end of the age; the angels shall come forth, and take out the wicked from among the righteous,
50 and will cast them into the furnace of fire; there shall be weeping and gnashing of teeth. (Matthew 13:47-50)
Fishermen were a common sight around the Sea of Galilee. They would bring their nets filled with fish to the shore and sort through the catch. What was worthwhile they kept, and what was not they threw away. So at the end of the age when the church has already been taken and God is dealing with Israel, Christ will return with the Angels and take away the evil from the good, and leave the righteous to remain on the Earth.
The New Testament and the Gospels differentiated the church, Israel, and the world. Jesus spoke this parable to the Jews and he was affirming a time of judgment is to come. For the Christian we have passed from judgment into life and what remains will be an evaluation of our works.