The study of e-participation is a young and growing discipline in which controversies are vibrant. One of these is the lack of a widely accepted definition of “e-participation.” Online political activities that involve little effort from the participant, such as liking or sharing political content on social media, are particularly divisive. Some scholars are reluctant to label expressive forms of online behavior as political participation. Others argue in favor of an adaptation of previous definitions to accommodate recent technological changes. Levels of engagement in different types of e-participation are increasing steadily over time. While differences between democracies are often stark, the upward trend has been consistent, especially since the emergence and expansion of social media. Whether this means that previously unengaged individuals are now taking part is one of the central questions of the literature on e-participation. To date, research has shown positive but modest results in support for a mobilizing effect. Particularly promising are findings suggesting that online tools are attracting younger participants to the political arena. Online forms of political engagement are often placed in a more general process leading to online and offline political participation. “Lean-forward” models that provide a contextualized understanding of the drivers and effects of e-participation are particularly insightful. In order to provide robustness to some of the questions that remain unresolved, scholars exploring eparticipation should consider expanding their methodological repertoires. The trend is toward mixed designs that combine surveys and other forms of data (big data collected from social media or qualitative data).