Light represents goodness and truth. Shining as lights in the world represents living in a good and rigtheous way so that people in the world can see that God is good and true. AT: "so that you will be like lights in the world" (See: [[rc://en/ta/man/translate/figs-metaphor]])
Here the word "world" refers to the people of the world. The words "crooked" and "depraved" are used together to emphasize that the people are very sinful. AT: "in the world, among people who are very sinful" (See: [[rc://en/ta/man/translate/figs-doublet]])