Public-private partnership as a new form of business draws attention of the academic community and the general public. However there is no clear understanding of what PPP stands for. The article considers the problem of formal definition of PPP and it’s role in contemporary economy. Similarities and distinctions between PPP and other forms of collaboration between private and public companies (e.g. privatization or public procurement) are revealed as a result of comparative analyses conducted in the article. Based on this analyses key features of PPP are formulated. Then there are considered causes and stimulus from participation of state and private companies in joint projects. Additionally there are given reasons for distinction between PPP and concession due to different level of risk transfer in these forms and different main source of income for private company. Special attention is given to the question of application PPP in infrastructure and innovations. As a result of the research the author has offered clarification for PPP definition and classification of PPP tools in Russia.