The dream that Santiago has is Egyptian pyramids and treasure.
Dreams are an important motif in the book. On a literal level, they are stories we take part in when we sleep. On a figurative level, they are who we want to be. Santiago is very dream-conscious.
It’s the possibility of having a dream that makes life interesting. (p. 11)
Santiago is obsessed with his dream, his own Personal Legend, and what it means. He seeks out mentors, like the old woman and the gentleman, who can explain it. He travels away from his shepherd’s home to pursue his dream and what it means, only to discover that his dream was waiting for him all along at home.