Fundamental mechanisms for electron production in ion‐atom collisions are reviewed. Electron emission is discussed in terms of categories involving zero, one and two atomic centers. The centers are defined as heavy nuclear charges which interact strongly with the ejected electron. The binary encounter process, attributed to zero or one center, is dominated by two‐body kinematics. The soft collision process, which corresponds to dipole transitions with small momentum transfer, is associated with one center. Various two‐center phenomena are discussed. Electron capture to continuum, giving rise to a cusp‐shaped peak near 0°, is viewed as a focusing effect in the Coulomb field of the receding projectile. Two‐center electron emission, involving the effect of both target and projectile charge on the outgoing electrons, is shown to be visible at forward as well as at backward emission angles. ©1996 American Institute of Physics.