How does a .desktop file differ from say a "symbolic link"?

With OpenSuse 11.1 (Kde 4.1.3), if I right click in say Dolphin I can create a new "Link to URL". If I understand correctly this in turns crates a .desktop file instead of a symbolic link. The effect seems the same - I can click on the .desktop file to start the app. Is this new .desktop file method somehow better than using traditional symbolic links?

I wanted to add a link to Dolphin to the Desktop Panel. It seems if I right click on the panel and choose "Add Widgte/Applet" (Im using a German version -"Miniprogram hinzufgen" - so Im not certain how these are called in English), Dolphin is not one of the choices. The only hack I could think of was to add it to QuickLaunch (but the icon is too small then).

Is it not possible to add links to applications (or even files/urls with associated apps) to the Desktop panel (if theyre not exposed a "wigets/applets" which say Firefox and Dolphin dont seem to be) ?

Thanks in Advance.