A class of desktop PCs known as All-In-One systems combines the display and components into the same slimline case. This has the major advantage of creating a system that's far more space-efficient, effectively taking up no more room than a standard desktop PC's display would do, and generally these are accepted as being far better looking.
All-In-Ones bridge a gap between the power of a normal desktop PC and the space-saving convenience of a laptop, with the flatpanel design enabling them to double as a TV - if equipped with a TV tuner - or play films and internet video.
Similarly to laptops - due to their reduced size - all-in-ones tend to have weaker 3D gaming performance than many full desktops. However look for models with NVIDIA or ATI graphics for reasonable performance.
A wide range of All-In-Ones are available starting with entry-level models that use the Intel Atom processor, suitable for web browsing and basic office work. At the other end of the scale there are high-end models with powerful quad-core and full-desktop specifications that can handle gaming and complex applications.
As a guide here are a few select examples of system specifications for different grades of systems: