Hi Anatoly,
RadChart is being replaced by RadChartView (which has lighter, faster charting engine), but the libraries for RadChart are still included in the release. It will remain there for legacy support, and most likely receive bug fixes going forward. It is recommended for all new developement to use RadChart View instead.
This link will bring you to the documentation about the change and the comparison between the controls.
If you need support or documentation for RadChart, you can find it
here.
Good Luck!
Lancelot