The dynamical theory of the edge excitations of generic fractional quantum Hall (FQH) states is summarized and expanded. The low energy effective theory of the edge excitations for the most general abelian FQH states (including spin-unpolarized and multi-layer FQH states) and some non-abelian FQH states is derived using several different methods. The propagators of the electrons and the quasiparticles are calculated for the above FQH states. The microscopic theory of the edge excitations for the Laughlin states is also presented. Some simple applications of the edge theory to the transport properties of the FQH states are discussed. In particular, the tunneling between edge states is shown to be a powerful tool to probe the internal topological orders in the FQH states. It can be used to distinguish different FQH states with the same filling fraction and to detect the non-abelian FQH states in experiments.