C1-C2-C3-C4 refers to a classification system used to categorize the levels of proficiency in a language, with C1 representing advanced proficiency, C2 representing mastery, C3 representing intermediate proficiency, and C4 representing basic proficiency. This system is commonly used in language learning and assessment to accurately measure and track one’s language skills. It allows individuals to set goals and track their progress as they strive towards fluency in a language. The C1-C2-C3-C4 system is widely recognized and used by language institutions and employers around the world, making it a valuable tool for those seeking to improve their language abilities.