This document discusses content-based instruction (CBI), which combines language and content learning. CBI principles reflect learners' needs for acquiring a second language. It involves studying language through subject matter, with the second language serving as the medium of instruction at any instructional level. The roles of students include creating groups, supporting each other, and taking an active role in learning. Teachers must be knowledgeable in the subject matter and able to share that knowledge with students. CBI has advantages like making classes more active and interesting, but disadvantages like students not understanding many words and getting confused between languages. CBI effectively improves English proficiency and teaches skills needed for various professions.