Newbie question about creating cabinets on a wall with pull feature

Real newbie question. I am designing my kitchen. So, I have a wall and I put a rectangle on it for a cabinet. When I pull the rectangle, the front face and sides come, but the wall in behind is gone. How do I indicate that the new rectangle is not a section of the wall but something new? Thanks.

You should learn about Groups and Components. Geometry in sketchup is made of edges and faces and they all stick together.
To separate things your wrap them up as a Group, this way they don’t stick together. There are special Groups called Components which are linked copies, edit one and all the copies edit too.
So having said that, make your wall a group, then draw your cabinet rectangle on the outside of the wall group and make it a group as well, then double click it to open for edit and pushpull.

Keep the wall and cabinet separate (like the real world). The cabinets and the wall are each components (or groups).

Or make the cabinet the wall