Animals with tails are extremely diverse. To figure out what kind of animal you're thinking of, I need more information!
Could you tell me:
* What does the tail look like? Is it long or short, bushy or smooth, prehensile (grasping), or just for balance?
* What kind of animal is it? Is it a mammal, a bird, a reptile, a fish, or an insect?
* What is the animal doing? Is it wagging its tail, swimming, climbing, or something else?
Once I know more about the animal's tail and its characteristics, I can help you identify it!