Gravitational Lensing is the focusing of Electromagnetic Radiation (EMR) by a massive body. The setup is called a Gravitation Lens. A Galaxy has the mass to lens a more distant galaxy or Quasar (QSO).
Gravitational Microlensing is the gravitational effect on electromagnetic radiation by a smaller body such as a star.
Angular Power Spectrum
Cosmic Lens All-Sky Survey (CLASS)