Invisible Applications Folder inside App


I have iMac 2GHz Intel Core 2 Duo, 2 GB RAM, OSX 10.5.4.
I noticed this after the 10.5.3 upgrade. Inside the applications folder there is an invisible file (no icon) labeled Applications Folder. Get Info reveals it to be a unix executable file. I'm a newbie, and not sure what it means. I checked an identical iMac, and there is no such "invisible" folder inside the applications folder. Why is it on one iMac and not on the other? Seems odd. Thanks ahead of time for any help.