Part I. Basics. 1. A brief introduction -- 2. Special relativity and extra dimensions -- 3. Electromagnetism and gravitation in various dimensions -- 4. Nonrelativistic strings -- 5. The relativistic point particle -- 6. Relativistic strings -- 7. String parameterization and classical motion -- 8. World-sheet currents -- 9. Light-cone relativistic strings -- 01. Light-cone fields and particles -- 11. The relativistic quantum point particle -- 21. Relativistic quantum open strings -- 31. Relativistic quantum closed strings -- Part II. Developments. 41. D-branes and gauge fields -- 51. String charge, electric charge, and particle physics -- 61. String thermodynamics and black holes -- 71. T-duality of closed strings -- 81. T-duality of open strings -- 91. Electromagnetic fields on D-branes -- 02. Nonlinear and Born-Infeld electrodynamics -- 12. Covariant string quantization -- 22. String interactions and Riemann surfaces -- 32. Loop amplitudes in string theory