To shed light on ultra-short laser interactions, we study the laser ionization processes leading to the energy absorption and reflection. In particular, we investigate the ratio of the energy deposited to the material to the total incident energy. The absorbed energy density is studied as a function of pulse width and laser intensity. It is shown that the maximum absorption takes place at a given incident laser intensity that is considered as ablation threshold. For pulses shorter than 100 fs, only a small fraction of laser energy is deposited to the matrix, causing heating and leading to the thermal and/or mechanical modifications of the target material. We connect these results with the electronic excitation and the ionization processes leading to the changes in reflectivity and consuming electron energy. The obtained numerical results explain several recent experiments.