The document discusses key variables that influence the teaching and learning of a target language, including context variables, presage variables, process variables, and the nature of language instruction. It analyzes different types of language instruction, including direct vs. naturalistic techniques, crosslingual vs. intralingual techniques, and analytic vs. integral methods. The document also discusses content-based instruction/teaching and its emphasis on using the target language for classroom instruction through integrating language skills and academic content.