The opinions of citizens are now being given ever-increasing consideration. Today, many government administrations have set up public participation processes as one more of the inputs required to make a decision on several aspects of governance. e-Participation initiatives make it easier for citizens to access such processes. At the present time, there is no clear and accepted field definition due to the wide diversity of theoretical proposals and the interdisciplinary nature of the initiatives, many of which have been developed ad-hoc. This paper reviews the present literature in the field of e-Participation by means of a systematic mapping of the research work carried out in the timeframe 2000-2019, together with some earlier relevant proposals in the area, with the aim of obtaining a conceptual guide to e-Participation components. This review analyses the findings and clusters the results into a conceptual e-Participation framework, which we call ePfw. The results show the diversity of the conceptualizations of many authors (25% on average) in the identification of tools, areas and levels in the field of e-participation and the almost null incorporation of fundamental aspects like trust, security, or transparency. We also found a lack of systems development (13.3%) that would prove and allow the proposed theories to be put into practice.