Key Points Introduction The CMS trigger system filters uninteresting events, keeping the budget high for the flow of interesting data. Computationally, a trigger is a CMSSW path, which is composed of several software modules. Trigger prescales allow the data acquisition to adjust to changes in instantaneous luminosity while keeping the rate of incomming data under control The trigger systems allows for the classification and organization of datasets by physics objects of interest Choosing a trigger The most reliable way of inspecting the trigger information is through the CMSSW HLT trigger tools. The details for a given trigger can be explored through the CMSSW configuration and/or C++ implementation. Getting trigger prescales Prescales can be extracted using the trigger tools in CMSSW and from the brilcalc tool. Glossary