Cell comes from the future like Trunks.  He comes from 24 years to be exact.  He apparently killed Trunks and took his time machine to the past, for Trunks had killed Android 17 and 18, and he needs them to get "perfect".  Cell has a tail that can absorb people (and androids).  He does get perfect, but Gohan goes...I'd rather not spoil it for you.  His first mode is an ugly mode, and his second form is even uglier, but his perfect form is slightly cuter.  Cell was the first enemy to put on a martial arts tournament as a battle ground.  He later turns it into ruins.  The reason why he is called, "Cell", is because he has the cells of all the most powerful fighters.   Goku, Vegeta, Krillin, Piccolo, Tien, and Freiza.  Like Goku and Vegeta, he gets stronger after every battle, like Piccolo he can regenerate himself, and like Freiza he can live anywhere.  Cell is very powerful.  One minor thing, he regenarates himself about 50,000,000 times, and it gets boring after a while.

My opinion:  Cell is one of my favorite villains.  He is powerful, plus he is cocky like Vegeta.  Here are some screenshots.