Comets vary widely in their appearance due to many reasons. Scores of comets fall into the inner solar system every year, and likely most go undiscovered. You can track and even discover these just by logging onto the SOHO (Solar Heliospheric Observatory) website as dozens can be seen falling into the Sun every year as they approach the the solar surface.

Comets used to be found by amateur astronomers that searched the heavens for these objects, but with today's technology they are being discovered by robotic telescopes either on or above the Earth. Comets "melt" as they approach the Sun, some more than others, and those that pass closer to the Sun and then if they manage to pass near to the Earth, can become very bright and the tails can grow to enormous lengths, but most comets are just tiny and faint fuzzies, but on those rare occasions, a comet can become quite spectacular that anyone can see with the naked eye.

Brighter comets will often have 2 tails, a blue tail that is known as an ion tail, and a yellow tail that is a dust tail, as a comet rounds the Sun the 2 tail diverge to point in different directions. The ion tail is pushed by the solar wind, but the dust tail usually lags behind. The closer the comet comes to the Sun, the tails will often be widely separated after rounding the Sun.