The KLOE experiment has provided precise measurements of the branching ratio of the main neutral and charged kaon decay modes, of the K-L and the K+/- lifetimes, and of the K-L vector and scalar form factors. We present a description of the above measurements and an overall fit of all our data, with particular attention to correlations. These data provide the basis for the determination of the value of the CKM matrix element V-us and a test of the unitarity of the quark mixing matrix. In addition our first measurement of the charge asimmetry in K-S semileptonic decays, A(S), gaves us the possibility to contribute to the knowledge of R(epsilon) and testing the CPT symmetry through the Bell Steinberger relation.