Studying particle collisions at ever higher and higher energies has led to a deep understanding of the elementary particles and the forces that act between them. With the Standard Model of particle physics, a relativistic quantum-field theory, a comprehensive and precise description of all phenomena involving strong, weak, and electromagnetic interactions (but not including gravity!), is at hands. However, its limits and possible extensions need to be explored. With the Large Hadron Collider (LHC) at CERN, the Higgs boson was discovered in July 2012 with 11 fb-1 (inverse femtobarn) of proton–proton collision data collected in Run 1 – from 2011 to 2012 – culminating in a success story of the Standard Model and leading to the 2013 Nobel Prize awarded to Peter Higgs and François Englert. The LHC was upgraded in the years 2013–2014, allowing for higher collision energies and collision rates. Over the course of Run 2 of the LHC – from 2015 to 2018 – the experimental collaborations collected 139 fb-1 of data for analysis. The physics analyses that have become possible with these data cover a vast program that include precision measurements of Standard Model physics and Higgs properties. In parallel, vigorous searches for physics beyond the Standard Model are undertaken. These contain searches for neutral and charged gauge bosons and for heavy resonances decaying in hadronic or leptonic final states. Searches for new symmetries in nature are conducted that predict yet to be found new particles and that could give hints on the nature of Dark Matter in the Universe. In this talk, I will give an easy to understand introduction to the principal ideas on which the Standard Model is built, with a strong focus on the Higgs mechanism and the generation of the masses of elementary particles. In a second part, I will highlight actual results from the ATLAS experiment at the LHC based on Run 2 data, and I will conclude with a brief outlook of new challenges for the decades to come.