We review the observed properties of the bright quasar 3C~273 and discuss the
implications of these observations for the emission processes and in view of
gaining a more global understanding of the object. Continuum and line emission
are discussed. The emission from the radio domain to gamma rays are reviewed.
Emphasis is given to variability studies across the spectrum as a means to gain
some understanding on the relationships between the emission components. 3C~273
has a small scale jet and a large scale jet. The properties of these jets are
described. It is also attempted to relate the activity in the small scale jet
to that observed in the radio and infrared continuum.