2D space-time curvature

Question

Actually, why is the space-time curvature considered 2D plane. As 2-D dimensional space-time curve is used to explain why moon revolves around the earth stating because the massive objects wraps the space-time curvature i.e bends it due to which low massive objects like moon revolves around the large massive objects like earth. So, here the space-time curve is considered 2 Dimensional. Is it really or am I missing some points over here. And I m newbie Relativity topic.

Answer 1

It is an analogy, as a 4 dimensional equivalent would be hard to draw, and if it was 3 dimensional, you couldn't see what's inside!