Generally, doors in the Bible represent the initial desires for good and concepts of truth that introduce us to new levels of love and understanding, and even to the Lord Himself. Since a “house” represents a person’s desires, affections and passions, the door serves to introduce true ideas that can put those desires into action.

In John 10:7, the door signifies the Lord, who is good itself and truth itself. (Arcana Coelestia 2356[2])

In Revelation 3:8; 4:1, the door signifies admission to the arcana of heaven revealed. (Apocalypse Explained 260[2])

The meaning depends on context, of course. For example, references to doorposts and lintels are making a distinction between introductory goods and introductory truths. And, in Sodom, Lot's house had two doors -- an inner one and an outer one. When, in Genesis 19:6, Lot tried to convince the men of Sodom not to attack the angels visiting him, he went outside the inner door, but stayed inside the outer door. There, the outer door represents a desire for good that is resistant to the falsity represented by the men of Sodom; the inner door represents true ideas springing from that desire for good. Someone nurturing a desire for good could be admitted through the first door, but would have to learn the truth about how to express that desire before being admitted through the second.

(References: Genesis 19)