AMBER is the General User near infrared focal instrument of the Very Large Telescope Interferometer. It is a single mode, dispersed fringes, three telescopes instrument. His limiting magnitude of the order of H=13 will allow him to tackle two dozens of extragalactic targets. His extremely high accuracy, in particular in phase closure and differential mode give good hope for very high dynamic range observation, possibly including hot extra solar planets. His relatively high spectral resolution will allow some stellar activity observations. Between this extreme goals, AMBER should have a wide range of applications including Young Stellar Objects, Evolved Stars, circumstellar material and many others. This papers tries to introduce AMBER to its future users and insists on what AMBER measures, how it calibrates it and how this could give the reader ideas for applications.