I. Foliations on Manifolds.- 1.1 Definitions and examples of foliations.- 1.2 Holonomy.- 1.3 Ehresmann foliations.- 1.4 Foliations and curvature.- II. Local Riemannian Geometry of Foliations.- 2.1 The main tensors and their invariants.- 2.2 A Riemannian almost-product structure.- 2.3 Constructions of geodesic and umbilic foliations.- 2.4 Curvature identities.- 2.5 Riemannian foliations.- III. T-Parallel Fields and Mixed Curvature.- 3.1 Jacobi and Riccati equations.- 3.2 T-parallel vector fields and the Jacobi equation.- 3.3 L-parallel vector fields and variations of curves.- 3.4 Positive mixed curvature.- IV. Rigidity and Splitting of Foliations.- 4.1 Foliations on space forms.- 4.2 Area and volume of a T-parallel vector field.- 4.3 Riccati and Raychaudhuri equations.- V. Submanifolds with Generators.- 5.1 Submanifolds with generators in Riemannian spaces.- 5.2 Submanifolds with generators in space forms.- 5.3 Submanifolds with nonpositive extrinsic q-Ricci curvature..- 5.4 Ruled submanifolds with conditions on mean curvature.- 5.5 Submanifolds with spherical generators.- VI. Decomposition of Ruled Submanifolds.- 6.1 Cylindricity of submanifolds in a Riemannian space of nonnegative curvature.- 6.2 Ruled submanifolds in CROSS and the Segre embedding..- 6.3 Ruled submanifolds in a Riemannian space of positive curvature and Segre type embeddings.- VII. Decomposition of Parabolic Submanifolds.- 7.1 Parabolic submanifolds in CROSS.- 7.2 Parabolic submanifolds in a Riemannian space of positive curvature.- 7.3 Remarks on pseudo-Riemannian isometric immersions.- Appendix A. Great Sphere Foliations and Manifolds with Curvature Bounded Above.- A.1 Great circle foliations.- A.2 Extremal theorem for manifolds with curvature bounded above.- Appendix B. Submersions of Riemannian Manifolds with Compact Leaves.- Appendix C. Foliations by Closed Geodesics with Positive Mixed Sectional Curvature.- References.