Long ago in days of yore, Google provided a plugin for the popular Eclipse integrated development environment, the better for aspiring mobile devs to work with their favorite IDE while making new apps. Months after the release of the stand-alone Android Studio version 2.2, Google is officially getting rid of support for the older IDE in favor of its own internal project. To be clear, Eclipse is still very much alive and in active development (it's not a Google program), it's just the plugin that's no longer supported.
All of the tools that are in the Eclipse plugin are present in Android Studio, which is a free download on Windows, Mac OS, and Linux. That said, I can understand that some developers will be upset - Eclipse is an all-inclusive IDE, and moving to Android Studio will certainly be a jarring adjustment for some. (Hell, I'm just a humble writer and I get bent out of shape when I have to use WordPress instead of Open Live Writer.)
Current projects built in Eclipse should still work well enough, but taking advantage of new Android features will be harder and harder from here on out. Projects can be imported into Android Studio with the File>New>Import Project menu.
- Android Developers blog