Provisional, tentative are comparable when they mean not final or definitive.
Something provisional is adopted only for the time being and will be discarded when the final or definitive form is established or when the need which called it into being no longer exists.
Provisional, therefore, is used to describe something made or devised while its permanent successor is in process of formation or construction or when circumstances prevent introduction of a corresponding definitive or permanent thing; thus, a provisional order of a government agency is one subject to review and revision by the legislative branch; a provisional license or certificate (as of a driver or a teacher) is one destined to be replaced by a permanent license or certificate if the holder maintains certain standards or meets certain additional qualifications.
Something tentative is of the nature of a trial or experiment or serves as a test of a thing’s practicability or feasibility.