What is '$data' in ngtable's HTML page
ng-table maintains it's own scope, and $data is the data which exists in this scope, rather than your full data set, which is on the scope of the page controller. It is the property that is populated by the getData() function call in the ngTableParams() object.
This usage and syntax is deprecated, and has been replaced entirely in the current ng-table source, which is now written in TypeScript as of v2.0.0.