Thank you for the opportunity to help you with your question!
The LAD is a hypothetical module of the human mind decided to account for children's innate predisposition for language acquisition or speaking. This was first proposed by Noam Chomsky in the 1960s, and the LAD concept is an instinctive mental capacity which enables a child to produce language.
Keep in mind that the LAD is only theoretical. There isn't a section of the brain with 'Language Acquisition Device' printed on it and a big button to turn on and learn to speak. Rather, the LAD is used to explain what are most likely hundreds or thousands of underlying processes that humans have in their brain that have evolved to make us particularly exceptional at learning and understanding language.
Please let me know if you need any clarification. I'm always happy to answer your questions.