Solar energetic particles are believed to originate from two different sources, solar flares and coronal mass ejections. These two sources are the most energetic particle accelerators in the heliosphere, as they can accelerate electrons from 10keV to a few MeV and protons from a few MeV to a few GeV. In this contribution, we restrict our presentation to the case of solar flares, by reviewing the key observations of solar energetic particles, as well as the theoretical acceleration models, such as wave-particle acceleration, DC electric fields, and shock acceleration. Finally, we present a new theoretical approach connecting the acceleration with the energy release during solar flares, which might lead to a global modeling of solar flare energetics.