Introduction; Part I. Kazhdan’s Property (T): 1. Property (T); 2. Property (FH); 3. Reduced Cohomology; 4. Bounded generation; 5. A spectral criterion for Property (T); 6. Some applications of Property (T); 7. A short list of open questions; Part II. Background on Unitary Representations: A. Unitary group representations; B. Measures on homogeneous spaces; C. Functions of positive type; D. Representations of abelian groups; E. Induced representations; F. Weak containment and Fell topology; G. Amenability; Appendix; Bibliography; List of symbols; Index.