2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/49518We review how experimental data collected at the HERA lepton-hadron collider have improved our theoretical and phenomenological understanding of the standard model, and specifically of its QCD sector.4 pages, no figures, latex with hep99 class files. Invited talk at EPS-HEP99 (Tampere, Finland, July 1999). References correctedHigh Energy Physics - Phenomenologytext