In this revised and extended version of his course notes from a 1-year course at Scuola Normale Superiore, Pisa, the author provides an introduction - for an audience knowing basic functional analysis and measure theory but not necessarily probability theory - to analysis in a separable Hilbert space of infinite dimension. Moreover, some details have been added as well as some new material on dynamical systems with dissipative nonlinearities and asymptotic behavior for gradient systems.