The document discusses input and interaction in second language acquisition. It defines input as the language learners are exposed to, such as from teachers, other students, and their environment. Comprehensible input is language that learners can understand. The document also discusses foreigner talk, teacher talk, interlanguage talk, and the input hypothesis. Interaction involves negotiation between two or more individuals that allows learners to receive feedback on their language production. Effective interaction strategies include slowing speech and requests for clarification.