  We provide a concise overview on transverse momentum dependent (TMD) parton
distribution functions, their application to topical issues in high-energy
physics phenomenology, and their theoretical connections with QCD resummation,
evolution and factorization theorems. We illustrate the use of TMDs via
examples of multi-scale problems in hadronic collisions. These include
transverse momentum q_T spectra of Higgs and vector bosons for low q_T, and
azimuthal correlations in the production of multiple jets associated with heavy
bosons at large jet masses. We discuss computational tools for TMDs, and
present an application of a new tool, TMDlib, to parton density fits and
parameterizations.
