  In modern High Energy Physics (HEP) experiments, triggers perform the
important task of selecting, in real time, the data to be recorded and saved
for physics analyses. As a result, trigger strategies play a key role in
extracting relevant information from the vast streams of data produced at
facilities like the Large Hadron Collider (LHC). As the energy and luminosity
of the collisions increase, these strategies must be upgraded and maintained to
suit the experimental needs. This whitepaper compiled by the SMARTHEP Early
Stage Researchers presents a high-level overview and reviews recent
developments of triggering practices employed at the LHC. The general trigger
principles applied at modern HEP experiments are highlighted, with specific
reference to the current trigger state-of-the-art within the ALICE, ATLAS, CMS
and LHCb collaborations. Furthermore, a brief synopsis of the new trigger
paradigm required by the upcoming high-luminosity upgrade of the LHC is
provided.
