A Ph.D. is a specific type of doctorate degree while a doctorate is an advanced post-secondary degree. A Ph.D. stands for doctor of philosophy, even though Ph.D.s can be earned in subjects that are not philosophy like hard science. This means that all Ph.D.s are doctorates, but not all doctorates are Ph.Ds.
A Ph degree typically allows the recipient to teach at the highest levels of education. Note that the meaning and significance of a doctorate degree is similar in most countries, but not the exact same. Ph are not necessarily more prestigious than other doctorate degrees like Doctor of Medicine or Doctor of Pharmacy.