In this talk I review the motivations and the prospects of the study of the scattering of W boson. The details of the mechanism of electroweak symmetry breaking (EWSB) that can be unveiled studying WW scattering will be presented. The issue of the extraction of on-shell \mbox{WW $\to$ WW} scattering amplitudes from the study of physical processes initiated by fermions, i.e. \mbox{qq $\to$ qqWW}, will be addresses using the effective W approximation (EWA). A discussion of the regimes of validity and of the expected corrections to the EWA will be presented together with a detailed comparison of the EWA to existing MC and analytical computations.