It is well established that the accretion disk and jet are coupled. Jet and accretion disk arise self-consistently from any transonic flow solution and clearly from its generalized version, the two-component advective flow (TCAF) solution. Observationally, strong signatures of disk-jet connections are seen for many black hole binaries. The nature and evolution of jets depend on accretion flows. Correlation between X-ray and radio fluxes is also seen, which indicates a coupling between accretion disk and jet. In this review, we discuss developments of theoretical models to describe the origin of the jets or outflows and the nature of the disk-jet coupling on the basis of the transonic flows around black holes. Then we discuss the observational evidences of the disk-jet connections.