Suicide is, very simply ending one's life, often due to some form of stress or pain in the individual's life. Suicide is viewed by some as completely reasonable and by others as selfish.
Certain individuals label suicide as reasonable due to the fact that it negates the pain and suffering an individual may be feeling that may not be tolerable or possible to deal with.
Suicide is also labelled as selfish because it ignores the responsibilities one has to others and the world. This usually falls under the category of those who realise that life is not based on the individual, because if it were jumping off a bridge wouldn't work since you'd land on the 22 story high pile of bodies already there. In this sense, suicide is seen as an escape harming the people close to one's self and adding trauma to their lives.
It is important to remember that many people who attempt suicide are not in fact suicidal and need something as simple as someone to talk to, therefore, judging or institutionalising someone who has attempted to commit suicide will contribute further to their problems.
An anti-suicidal quote: "You can't possibly know if life will get better if you aren't here to live it". That one kept a number of people here.
A form of suicide is jumping off a bridge, or in front of a train, much to the inconvenience of commuters. This form is often a final "screw you" to the world.