The following two default p2 update sites are usually included in Eclipse, what is the difference between them ?
Some content exists in both repositories (e.g. Eclipse PDE Plug-in Developer Resources
), some only in one of them (e.g. Junit Test runner client for UnitTest View
).
The last option in the dropdown is the URL for the 4.27 release of the Eclipse Project. It's the top-level project that produces the Platform, Java tools, and Plug-in Development Environment, that together form the Eclipse SDK. It's what most people think of when they think of Eclipse.
It's not the only one that provides an Update Site, though, and although the list that makes up the rows on https://www.eclipse.org/downloads/packages/compare is a little dated, it's quite common to want more to work with inside the workbench than just the Java and Plug-in tools. That raises the question of how you can find those other tools, and find releases that work on, and ideally have been explicitly tested with, Eclipse 4.27? And then do it again when 4.28 comes out?
Enter the 2023-03 URL in your dropdown, the current URL for the quarterly coordinated Simultaneous Release. Since 2006, I think, there have been regular releases put together by the projects themselves (with some help) to offer both combined downloads in different flavors, and a central URL that could be used to install all of their content (typically never recommended, but one man dared). They used to go by the names Callisto, Helios, Juno, and other celestial bodies, but once the effort settled into being quarterly and we got tired of voting on names, the date became the thing (along with latest).
Not everything from every project shows up in the coordinated release URL, though. Participation isn't mandatory, and some participating projects don't want their source and test features (or something called the "JUnit Test runner client for UnitTest View") cluttering things up in the coordinated site. For most people who will only ever use the tools, and maybe begrudgingly report bugs through the proper channels, it's not going to be an important distinction.