The difference as I understand it is that Euthanasia is a concept based on a belief of limiting life span, either due to criteria based on age, or disease, or variations therof. Assisted Suicide, as the name implies, means the active assistance given to one individual to end their own life. The difference is, believing in the concept of Euthanasia involves thought, belief and theory, the second involves a practical act, which in this country is illegal, although there is an increasing school of thought that believes that any individual should have the right to die if they wish, including those who are unable to end their lives by their own actions.