What does Matthew 1:20 mean?

But while he was thinking about this, an angel from God appeared to him in a dream and said, 'Joseph, descendant of David, don’t be afraid to take Mary as your wife. The child she’s carrying is from God’s Spirit.' Matthew 1:20 - Modern Text Bible

(God intervenes through a dream, reassuring Joseph and explaining that Mary’s pregnancy is miraculous, not shameful.)