CLIL (Content and Language Integrated Learning) refers to teaching subjects in a foreign language to support students' language skills alongside their mastery of course content. The document discusses the history of CLIL in Europe over recent decades and centuries. It also examines definitions of CLIL, different forms it can take in education systems, and considerations around who can be a CLIL teacher. Effective CLIL teachers require strong skills in the target language plus strategies for supporting students, though they do not need to be language specialists.