I present an overview of the physics of the Josephson effect between Bose condensed systems, with emphasis on the recently achieved BECs in trapped alkali gases. I focus mostly on those physical phenomena that are likely to be observed only (or more
easily) in these novel systems. Thus I omit the discussion of problems which may be viewed as straightforward applications of well known Josephson physics. In particular, I review the external and the internal Josephson effects, and discuss how in the latter case it may be possible to explore the crossover between collective Josephson behavior and independent boson Rabi dynamics. I also describe novel macroscopic quantum phenomena such as self-trapping and interference between separate Bose condensates.
