This document discusses the difference between learning and acquiring a language according to Stephen Krashen's theories of second language acquisition. Krashen believes that language acquisition does not require explicit grammar rules or drills, but rather occurs through meaningful interaction and natural communication where the focus is on message conveyance rather than form. The document then provides a brief overview of Krashen's key hypotheses, including that adults acquire language similarly to children, input and immersion best facilitate unconscious learning, and that affective factors like anxiety can prevent input from reaching the language acquisition device.