Public-Private Partnerships (PPPs)provide a new 'model' for infrastructure servicedelivery, which combines elements borrowed from other legaleconomic and financial structures. A mixture of elementsderived from public procurement, project finance, concessioncontracts, and policy network theories provides thebackground for PPPs structures. PPPs not only articulatesuch elements in one product but also constitute separateevolutions of the structures they originate from. In part,PPPs have been created to solve some problems those domainshave generated or were not able to solve efficiently.However, PPPs are not meant to replace those domains but toprovide alternative options to them. The natures of PPPs areassociated with a new contract, procurement and relationshiptype. For some, a PPP is a new 'contract type'whose main characteristics are risk sharing between thepublic and private party; bundling of construction andoperation; output base specifications; and long termcommitments serve to define and distinguish the type othersPPPs as a 'procurement type', alternative totraditional public procurement (including outsourcing), andconcession. For some others, PPPs constitute new'relationship types' between the PublicAdministration (PA), private parties and stakeholdersinvolved in an infrastructure service delivery project.Indeed, a PPP is all of the above: a new contract,procurement, and relationship type. The origin of thesetypological diversities is mainly due to the differentperspective legislators, practitioners, and scholars havehad toward PPPs.