The simplified command-structrure is:
| {begin | include | exclude}
"include" shows only lines that contain the regular expression.
"exclude" shows only lines that not contain the regular expression.
The "or" comes into play with the regular expression. That's a pattern which descibres what you want to filter.
In this case it's a simple one, it means "Gi0/1" OR "Fa0/5" (OR = "|")
General information about limiting the output of show-commands you can find here:
http://www.cisco.com/en/US/docs/ios-xml/ios/fundamentals/command/show_through_show_fm_summary.html
Information and examples about Cisco's regular expressions:
http://www.cisco.com/en/US/docs/ios/12_2/termserv/configuration/guide/tcfaapre_ps1835_TSD_Products_Configuration_Guide_Chapter.html
At first it might seem complicated but iIt's worth obtaining some basic knowledge of regular expressions - that's what the CLI makes much more powerful than any GUI.
HTH
Rolf
