A thorough understanding refers to a deep and comprehensive knowledge or grasp of something. It means having an in-depth awareness of all the key aspects, details, and intricacies involved in a particular topic or situation. A person with a thorough understanding is able to see the bigger picture, connect different pieces of information, and make informed decisions based on their complete comprehension. In other words, it means going beyond surface-level knowledge and delving deeper into the subject matter to gain a deep and rich understanding.