The current standard model of cosmology, known
as $\Lambda$CDM, has a solid observational basis, but requires
the existence of two exotic entities, that sum a 95$\%$ of the
matter-energy content of the Universe.These components are dark
matter, of absolutely unknown physical nature, and dark energy, that
is explained as the cosmological constant in $\Lambda$CDM. A full
understanding of these dark entities is the main goal of
the current cosmological activity. One of the leading projects
in this task is the Dark Energy Survey (DES), an optical and near
infrared galaxy survey that has imaged 5000 deg$^2$ of the southern
celestial hemisphere in five broad bandpass filters. The survey
observations started in 2013 and were completed in early 2019. DES
studies the dark energy properties using four independent
methods: number counts and spatial distribution of galaxy
clusters, weak gravitational lensing, galaxy clustering including
baryon acoustic oscillations and distances to supernovae Ia. The
four measurements are performed using the same data set, with the idea
of ensure a very strict control of the systematic uncertainties. Here, the
first cosmological results, using data taken during the first season of the
project, are presented. For the first time, the precision level from a
galaxy survey is similar to that coming from the study of the CMB, opening
a new era on cosmology.