What does this do? gacutil /l | find /i ?about?

gacutil.exe is used to install strong typed assembly in GAC.

gacutil.exe /l is used to lists the contents of the global assembly cache.

|(pipe) symbol is used to filter the output with another command.

find /i ?about? is to find the text ?about? on gacutil output. If any lines contains the text ?about?

 then that line will get displayed on console window