"Let's take a nap" is an informal suggestion or invitation to rest or sleep for a short period of time. It can be used in various contexts, such as when you and someone else are feeling tired and want to relax together. It implies a casual and comfortable atmosphere, making it a friendly way to propose a brief break from activities. So, if you're feeling a bit weary, just say, "Let's take a nap," and enjoy some revitalizing rest.