  This paper introduces a list of observations related to the beam-beam
interaction that were collected over the first years of LHC proton physics
operation (2010-12). Beam-beam related effects not only have been extensively
observed and recorded, but have also shaped the operation of the LHC for
high-intensity proton running in a number of ways: the construction of the
filling scheme, the choice of luminosity levelling techniques, measures to
mitigate instabilities, and the choice of settings for improving performance
(e.g. to reduce losses), among others.
