Im using the opengeo stack, and want to double check my understanding of each element.

• PostGIS - The database for storing my data
• GeoServer - The link between the online part / the database

Here's where I am not fully sure:

• Geoexplorer, viewing, editing data visually in the POST database
• Client SDK - The same as geoexploer but I have to add the functionality?

If I want to add Graphs to the map, i.e. the user clicks on a point, how would I go about that? using SDK and the GeoEXT?