CMB anisotropies: Cosmic confusion and polarization

Some physical effects producing Cosmic Microwave Background (CMB) anisotrop ies are briefly described. The CMB angular power spectrum is calculated -in appropriate cases- with the essential aim of estimating and comparing the effects produced by reionization and gravitational waves; thus a problem of Cosmic Confusion is pointed out. Accurate measurements of the CMB polariza tion could solve this problem in future. Some comments about the PLANCK mis sion -ESA project for anisotropy detection- are given.