In this contribution, we describe the operation of metasurfaces and their opportunities to produce innovative antenna solutions. Classical categorizations describe metasurfaces in terms of the operational frequencies, such as optics and microwaves. Another important categorization is based on the active or passive operation of metasurfaces. In this contribution, we make a classification based on their principle of operation. Specifically, we sort them out in four groups. First, there are metasurfaces that use Huygens' principle to manipulate wave fronts. Second, some metasurfaces inhibit the propagation using electromagnetic bandgaps, which are used for example, to produce gap waveguide technology. Finally, there are metasurface antennas whose radiation properties are controlled with two-dimensional leaky-waves and two-dimensional lenses.