Blue jets and gigantic jets are transient luminous events in the middle atmosphere that form when conventional lightning leaders escape upward from thundercloud tops and propagate toward the lower ionosphere. Petrov and Petrova  first expressed that jets could be the extension of classic lightning discharges initiated within the cloud boundaries. This dissertation demonstrates the fundamental physical similarities between the various electrical discharges known to occur in the thundercloud due to local and global charge imbalances. How charge imbalances form in the thundercloud has been first suggested by Wilson , but their impact on the occurrence of blue and gigantic jets was not explored. This work shows that the accumulation of screening charges near the thundercloud top produces a charge configuration leading to the initiation of blue jets, and the effective mixing of these charges with the upper thundercloud charge to that of gigantic jets. Also, the physics of lightning and jets, and many of the small-scale features observed in jets can be interpreted in terms of streamers (needle-shaped filaments of ionization), and are further explored via numerical modeling.