The Mozilla Foundation is an organization that supports the various Mozilla projects such as Firefox, Thunderbird and various other software. Most Mozilla products support the use of Add-ons to add functions to the software, these function are added by using XPI files which are a derivative from the XPInstall Technology which is able to install over various platforms for Mozilla products.
XPI files which are similar to Zip files usually contain the following.
» Install script
» Data files
Due to the similarity to Zip files it is possible to open these files by changing the file extension from its usual .xpi to .zip.