  The latest Planck results on the power spectrum of the Compton-$y$ parameter
are the most accurate probe of the thermal Sunyaev Zeldovich (tSZ) effect
caused by resolved and un-resolved clusters of galaxies. On large angular
scales, the power spectrum amplitude is mostly due to the statistical
distribution of clusters in the sky and therefore is an indirect probe of the
clustering of matter, $\sigma_8$, as well as the angular diameter distance that
depends on other cosmological parameters such as the Hubble parameter, $h$, and
the matter density $\Omega_m$. Here I discuss the constraining power of the tSZ
power spectrum, in light of the Planck Compton-$y$ map data, and our current
understanding and measurements of the intra-cluster medium.
