Challenge Rating

Source: D&D 5.2 SRD Rules Glossary

Challenge Rating (CR) summarizes the threat a monster poses to a group of four player characters. Compare a monster's CR to the characters' level. If the CR is higher, the monster is likely a danger. If the CR is lower, the monster likely poses little threat. But circumstances and the number of player characters can significantly alter how threatening a monster is in actual play. "Gameplay Toolbox" ("Combat Encounters") provides guidance to the GM on using CR while planning potential combat encounters. See also "Stat Block."