Solid core doors are solid from front to back. The typical solid core door is a mixture of wood particles glued together with heat, resins and hydraulic pressure to produce a uniform, consistent product.  The doors are primed ready for painting and can be painted any colour 

 

Semi Solid core doors are manufactured using a similar process as the Solid core doors however you will find some cavities, Within the door ,

 

Both of the aforementioned doors will offer an improvement on white moulded doors in terms of durability, thermal efficiency and noise reduction