The phrase "chill" has multiple meanings depending on its context.
1) As an imperative, it can be used to tell someone to relax or calm down, as in "Don't worry about it, just chill."
2) It can also refer to a state of being cooler than usual, both literally and figuratively, such as when describing a room that is too cold or an emotional state where one feels uninvolved or dispassionate.
3) In its informal usage, "chill" means to relax, hang out, or spend time with friends, often in a casual setting like watching movies or listening to music. For example: "Let's just chill tonight and forget about work."