A design is a commercial property right, which assigns an exclusive right of use for an esthetic design - meaning the outer appearance of products - to its proprietor.
As designs, you could protect:
Two- or Three-dimensional appearances, with a certain design or color, form, shape, material, logos, icons, surface structure (e.g. the outward appearance of a mobile phone, an electrical device, a handbag, a lamp etc.).
BUT: No computer programs, no appearing attributes that only depend on their technical function, or those having to be rebuilt to enable the construction of another product.
Read more about What is a Design?