How does the potential get from A to B in a plasma?

Solutions to the question of how the plasma potential varies from point A to point B, at which the values are specified, are discussed. Each answer depends on plasma and boundary conditions. Plasma potential structures measured by emissive probes are considered. Examples include potentials associated with sheaths and presheaths in collisionless and collisional systems, unmagnetized and magnetized double layers with single and multiple step transitions, semiconductor etching and rf self bias, tandem mirror plasma confinement and tokamak antenna impurity production. DC structures, time average structures associated with capacitive and inductive rf and the role of potential well pumping are considered.>