Cyborg: In most cases, the biggest difference between characters is determined by whether or not someone is an alien or a Android. Android is just another word for "Cyborg". Cyborg is a type of robort or a BOT that is half machine and half flesh or full machine or just part machine and rest flesh.

TioPiePie:
The first cyborg to appear was Tao-pie-pie, who had himself rebuilt mechanically in time for the 23rd Tenkaichi Budokai. His implants included an energy cannon, eye lenses, an extendible sword and mechanical limbs.

Freeza Bot:
The second cyborg was Freeza, who had himself rebuilt after losing to Goku and getting blown up along with the Planet Namek. His implants only served to keep his body together.

Dr Gero's Androids:
The next batch of cyborgs were created by Dr. Gero as part of the artificial human series he was making for the Red Ribbon Army. These cyborgs were far more powerful than anyone the Z fighters had ever faced before, and in Trunks's time line they were able to kill nearly everyone on the planet. For Example: Android #16, Android #17 and Android #18 made earth a living hell in Trunks' time line. In the present time line Perfect Cell is (or was) strongest cyborg.

Fact on Cyborg:
Cyborg are tireless and able to fight all day; they are also nearly invulnerable and virtually impossible to harm.

About Cell:
Power absorbing cyborgs are a special case. Cell is one such example. He can absorb incoming ki attacks as well as drain ki from someone directly or absorb the whole person. Cell is one of the most strongest cyborg because he uses powers such as Absorption, Dispel and Suppress.

Android #18:
Due to their origins, cyborgs could have such advantages as "they do not bleed" as well as such disadvantages as "their body doesn't heal in case of BODY DAMAGE". As a side note, Android #18 contains sufficient organic parts to give birth to a daughter sometime after the destruction of Buu and the Tenkaichi Budokai presented in Buu Saga.

I haven't seen the whole Buu Saga just part of it so I am not sure on this but it was stated somewhere that a wish was made to make Android #18 human. Because if she wasn't human she couldn't have had a daughter (Bra) with Krillin.