  At the LHC all processes are QCD ones, whether "signal" or "background". In
this review the frontiers of current QCD research are addressed, towards
increased understanding, improved calculational precision, and role in
potential future discoveries. Issues raised include the limits of perturbative
QCD calculations and parton distribution usage, the nature of multiparton
interactions, the impact of colour reconnection on physical observables, the
need for progress on hadronization modelling, the improvements of parton
showers and their combination with the matrix-element description, the use of
QCD concepts in Beyond-the-Standard-Model scenarios, and the key position of
event generators and other software in the successful exploration of LHC
physics. On the way, several questions are posed, where further studies are
needed.
