Along with registration charge we also have compulsory third party insurance, which covers injuries to third parties ie passengers or people other than the two vehicle operators (1st and 2nd parties). When we say 'rego' we generally mean both registration and third party insurance as in most states it's paid to the RTA as part of the same transaction even though the insurance part goes to the actual insurer. Vehicle insurance covering damage or theft is different and separate and up to the individual - as in the US.