The phrase "big difference" means a significant distinction or separation between two things. It refers to something that is noticeable and substantial, making an impact or altering the situation in a considerable manner. The term can be used positively or negatively depending on the context - for example, it could mean a positive change such as improving one's life or achieving success, but it could also imply a negative outcome like causing harm or failure. Overall, "big difference" signifies an important and observable variation between two states or conditions.