To unfold is to open or reveal, the way a small square of paper might unfold into a large map, or the way the plot of a mystery novel can unfold into a clear picture of who the killer is.
Anything that's folded or compacted unfolds as it opens up and stretches out. So a yoga teacher might curl into a tight ball and then unfold his limbs, stretching them wide. Or you might unfold a tightly sealed secret note or a gently creased letter from your grandparents. Information can unfold figuratively, too, or become more open and clear: "As the details of the crime began to unfold, the detective got ready to make an arrest."