RePEc’s mission is about the dissemination of research in Economics. Publishers (commercial, non-profit, academic, or policy institutions) offer metadata about their publications and RePEc then “takes care of it.” How?
Basically, RePEc makes the data available, and then is it up on others to build user-facing services with that data. Some of those services collaborate with each other by enhancing the data and exchanging it among themselves. Those can be identified by being in the repec.org domain, like EconPapers, IDEAS, NEP, RePEc Author Service, etc. These in particular exchange usage data that allows to get a picture of how much RePEc data is used, through LogEc.
But there is more. RePEc data is leveraged by many other sites. While the resulting use and traffic is not reported, and we thus have no idea how much RePEc data is used there, these other sites are contributing to the research dissemination mission of RePEc. To take a few examples: Econlit and EBSCO use RePEc data for working papers, Google Scholar and ORCID got started with data dumps from RePEc. Some resort to scraping RePEc websites instead of using the original data (which is freely available), such as ResearchGate as well as a myriad of new sites targeted towards researchers.
In the end, this is what it is all about: a publisher indexes its publications in one spot, and from there it gets widely disseminated. This is what RePEc is all about.
The RePEc Blog 