Android 13 - he was one of the androids Dr. Gero was working on when he was killed by Android 17. He set out to kill Goku. He fuses with Androids 14 and 15 to become one big and strong Android. Before he powers up he looks like a redneck, he wears a RR hat and calls Goku a "city slicker", but when he fuses with Androids 14 and 15 he turns blue with orange hair and powers up enormously. Goku kills him in Movie 7 after absorbing his spirit bomb in SSJ1.
Android 14 - Dr. Gero created him along with Androids 13 and 15. He is very small and wears a geen coat looking robe. He is all purple and has a drinking problem. Vegeta kills him in Movie 7.
Android 15 - Dr. Gero created him along with Androids 13 and 14. He is moslty gray and has long black hair tied into a ponytail. Trunks kills him in Movie 7.
Android 16 - he was created by Dr. Gero and then stored. He was opened by Androids 17 and 18. As it turns out though, he is peaceful and loves wildlife. His sole purpose was to kill Goku, but he never did. He fights Cell and gets half of his head blown off, but is put back together and repaired by Bulma as a Z fighter. Android 16 was destroyed again and that was what triggered Gohan to go SSJ2.
Android 17 - Dr. Gero created him as the android brother of Android 18. Android 17 ends up betraying and killing Dr. Gero. While fighting Cell, he gets absorbed by him. However, at the end of the Boo saga he returns as a good guy. In GT he fuses with Artificial 17 to become Super 17.
Super 17 - Dr. Gero and Dr. Myuu created him in hell. He escaped through a portal to earth. He fuses with Android 17 to become Super 17.
Android 18 - Dr. Gero created him as the android sister of Android 17. Android 18 has the same evil qualities as her brother. She also got absorbed by Cell, but got spit back out. Later, she marries Krillin and has a daughter named after Krillin's ex-girlfriend Marron.
Android 19 - he was a fat Android, created by Dr. Gero. Android 18 has the power to absorb his opponent's energy. He was later killed when Vegeta blew off his head.
Android 20 - he was Dr. Gero.
Android 21 (Cell) - was Dr. Gero's best creation, is made up of cells of the finest fighters in the universe. (Mostly on Earth, but he has Frieza cells in him to)