What is a substantive position in public service?

I loathe to be negative; however, from many years of experience as a non substantive employee (casual in the Tafe sector), I believe a substantive position in public service is seen as 'one of far greater value' to a non substantive one . Sad really! Especially when substantive employees, who you deem to be non- discriminative, sub-consciously get on the bandwagon and sometimes act more superior.