Mapserver Itasca Application is a Thin Client Architecture. To display the image map data, that cannot be processed. User cannot access raw data. The main work is the responsibility of the server while the user can use zoom in, zoom out, pan, query a feature.
OpenLayers KML is a Thick Client Architecture. Raw data can transferred for analyze and can accessible to real data. user can order commands to get more than work, zoom in, zoom out, pan and query a feature. Thus, User get information by popup and can use Render, Display, Query and Process more data.