Final answer:
While all comets have certain inherent features like a nucleus, an orbit, and they contain dust, not all of them have a visible tail. Tails develop as comets approach the Sun and can vary in visibility, with some comets exhibiting two types: a dust tail and an ion tail.
Step-by-step explanation:
The comet's tail is something that some comets have, but not all comets display visibly. All comets have a nucleus and orbit, and they also contain dust. However, when it comes to the comet's tail, these are not always visible. The creation of a tail occurs as a comet approaches the Sun, with the tail consisting of gas and dust from the comet's head, or coma. This tail is an extension of the comet's atmosphere, which gets ionized or pushed out by the sunlight and the solar wind, causing the comet to sometimes have two different tails: a dust tail and an ion tail.
The brightness and visibility of these tails can vary among comets. This variation depends on factors like the comet's size, composition, and distance from the Sun at the time of observation. Therefore, while most comets develop tails when they are close enough to the Sun, not every comet has a tail that is visible from Earth.