An invention patent must meet a series of requirements to be granted: it must be novel, involve inventive step (does not constitute obvious solutions for one having ordinary skill in the art in the subject-matter), and present industrial applicability, i.e., it can be elaborated, reproduced, and manufactured industrially.
The major difference between a patent and a utility model lies in the inventive step because a utility model in itself implies the requirement of less creativity and technical complexity. For that reason, utility models focus more on small inventions that cover basic needs but lack technical complexity and are often based on other already existing know-how. This is the case for certain objects, small tools, implements, and instruments which, whilst constituting inventions, are simple improvements of the state of the art.
This is why utility models are often referred to as utility innovations or small patents. This is also why the maximum duration of utility models is, as mentioned, 10 years, i.e., half that of a patent (20 years). The utility model is not an alternative that exists in all countries. However, it exists in Spain, and it is further possible to switch the type of registration (from a patent to a utility model, or vice versa).