Hi JoZy,
In ArcGIS Silvrlight api we have MapPoint Class but in ArcGIS api for Javascript we don't have mapPoint class.But point class is there in ArcGIS api for Javascript this will accomplish your job .
var point = new esri.geometry.Point( {"x": -122.65, "y": 45.53," spatialReference": {" wkid": 4326 } });
params.geometries = [ point ];
Mr.JoZy your are from which part of world,I am from INDIA