Dear Peng,
Connection type means, SAP system can be connected by user as well as another 3rd party system. Whenever it got connected by user it will show as GUI, if 3rd party system connected it will show different.
Check http://help.sap.com/saphelp_nwpi711/helpdata/en/48/99b996ee2b73e7e10000000a42189b/content.htm
R,
Amala