Homicide refers to the act of a human killing another human

Human

Humans are the only living species in the Homo genus...

. Murder

Murder

Murder is the unlawful killing, with malice aforethought, of another human being, and generally this state of mind distinguishes murder from other forms of unlawful homicide...

, for example, is a type of homicide. It can also describe a person who has committed such an act, though this use is rare in modern English. Homicide is not always a punishable act under the criminal law, and is different than a murder from such formal legal point of view.
Criminal homicide takes several forms and includes certain unintentional killings.