The document discusses several key aspects of language structure and learning a second language, including: 1. Language is complex, dynamic, and arbitrary but humans have an innate ability to learn language regardless of background. 2. Phonology and pronunciation can be difficult for second language learners, as some sounds do not exist in their native language. 3. Morphology examines the smallest meaningful units of language, including free and bound morphemes that can derive new words. 4. Syntax, semantics, vocabulary, and nonverbal communication like gestures can also present challenges for English language learners from different linguistic and cultural backgrounds.