This is a short presentation to the capability of the freefem++ software, in section 1, we recall most of the characteristics of the software, In section 2, we recall how to to build a weak form form of an partial differential equation (PDE) from the strong form of the PDE. In three last sections, we present different problem, tools to illustrated the software. First we do mesh adaptation problem in two and three dimension, secondly, we solve numerically a Phase change with Natural Convection, and the finally to show the HPC possibility we show a Schwarz Domain Decomposition problem on parallel computer.