The document discusses several key differences between how a first language is acquired compared to a second language. It notes that a child acquires their first language through natural exposure and practice from birth, while second language acquisition for adults involves a formal classroom setting. Additionally, a child's brain is still developing during first language acquisition, making it easier for them to pick up language skills naturally, whereas an adult's brain is already lateralized and less plastic. Pronunciation and accents are also generally more difficult for adult second language learners to acquire compared to children due to already developed speech patterns in their first language.