Magnetic reconnection process is reviewed with particular emphasis on its physical impacts on plasma confinement and acceleration. In the first place, heuristically discussed are the existence and importance of some violent process in laboratory and space plasmas that breaks the frozen-in principle; this is the magnetic reconnection process. It cuts and connects the magnetic surface, accordingly, plasma particles separated by the surface are mixed up and those residing in the same domain are separated out. On occasions, plasmas are explosively accelerated. In the second place, the topological condition for magnetic reconnection is given and the strength of reconnection is defined. Then, two basic theoretical models leading to reconnection, Petschek model and tearing mode instability, are described as representatives of explosive acceleration and plasma mixing, respectively. Finally, some examples of numerical simulations on externally driven reconnection and tearing instability are presented.
