"plans" means 2D overhead views of a 3D model. "sections" means 2D side views of a 3D model, like a cross-section. I don't know what "real-time" means here, but I'd bet that it means you can grab onto the plane that defines the cross-sectional cut, move it in the normal direction, and have the model update smoothly. (The non-real-time alternative is that the location of the plane is specified by a value in some dialog box.)
"plans" means 2D overhead views of a 3D model. "sections" means 2D side views of a 3D model, like a cross-section. I don't know what "real-time" means here, but I'd bet that it means you can grab onto the plane that defines the cross-sectional cut, move it in the normal direction, and have the model update smoothly. (The non-real-time alternative is that the location of the plane is specified by a value in some dialog box.)