1. Introduction; Part I. Short Excursion: 2. Central charges in superalgebras; 3. The main building blocks; Part II. Long Journey: 4. Non-Abelian strings; 5. Less supersymmetry; 6. Non-BPS non-Abelian strings; 7. Strings on the Higgs branches; 8. Domain walls as D-brane prototypes; 9. Wall-string junctions; 10. Conclusions; Appendixes; References; Index.