What information does Pip give Magwitch? Why does he withhold information about Compeyson? What does this reveal about Pip?

Pip warns him that he is in danger of being discovered, and that they must be very careful. Pip tells him that they won’t be able to see each other or talk very often, but that Herbert will communicate between them. Pip leaves out certain information because he doesn't want to burden poor Magwitch too much. This shows Pip's very soft and thoughtful side.