The Kentico REST service allows you to obtain data of any object or page within the system, and also to modify these objects. To enable the service, replace <modules> with <modules runAllManagedModulesForAllRequests="true"> in your web.config file and enable the service in Settings -> Integration -> REST.
The example on this page loads XML data of the first 10 cms.country objects in the system using the following REST request: ~/rest/cms.country?topn=10&columns=CountryID,CountryName,CountryDisplayName
The result is displayed in a table.
See the code of the ~/CMSWebParts/GridForRESTService.ascx web part for technical details. Full documentation of the REST service can be found in Kentico REST service.