Darkness" is a state without light. "Light" is truth from the Lord, so "darkness" represents a state where truth is lacking. Here's a cogent passage from Arcana Coelestia: "The person who has yet to be regenerated is called 'a void and an empty earth', and also 'ground', in which no good or truth at all has been sown - 'void' where there is no good, and 'empty' where there is no truth. Consequently there is 'thick darkness', or stupidity and lack of knowledge about anything that has to do with faith in the Lord and so anything that has to do with spiritual and celestial life. (Arcana Coelestia 17)

2246. 'They went towards Sodom' means concerning the human race which was immersed in such great evil. This is clear from the meaning of 'Sodom' as evil that stems from self-love, dealt with above in 2220, and of 'looking towards the face of Sodom' as towards the state of the human race, 2219. The reason 'Sodom' means the state of the human race which was immersed in such great evil is that Sodom is not used to mean Sodom but all those throughout the world who are governed by self-love; and the description of Sodom represents the state of all who are immersed in that evil, as becomes clear from what follows. The fact that self-love is the source of all evils, and so of evil itself, is clear from what has been stated and shown about it already in 2045, 2057, 2219. This is why it is said here that they were immersed in such great evil.