With INTERACT, you have several files to keep track of, but only the *.xiact file is vital:
data-files - (*.xiact) Your observational data is completely stored in those files. This are stand-alone files text files and are all you need, when it comes to exchanging, extracting or analyzing observed behavioral data. Those files can be stored anywhere in your file system. If you want to take your work with you, you can store them on your CodeMeter Stick.
Code definition files - (*.ikey) Manually defined Code definitions with corresponding shortcuts and Classes are stored in code definition files, preferably stored under '..\Mangold INTERACT Data\CodeDefinitions', but anywhere else is fine too. Those Code definitions are created and edited through the Code definitions window.
Code Archive files - (*.icar) An automated collection of project specific Classes and Codes is stored in Code Archive files. Each data-file is linked to such a Code Archive. Files of the same project or study, that is based on the same set of Codes, share the same Code Archive. It serves as a kind of analysis template, because it ensures an identical structure in the statistics and the use of the same colors for a Code in different charts. *.icar files need to be stored in '..\Mangold INTERACT Data\CodeArchives'!
Document Templates - (*.atp) Predefined templates that contain project specific defaults. You can predefine virtually everything available in a document, from various file properties, a predefined structure of DataGroups and DataSets or all Classes needed in a specific order. If a template is stored in the ..\Mangold INTERACT Data\Templates folder it can be called through the command Start - Files - New > New from template.... For further information, read Create a Template.
Chart contents - (*.tee) The appearance of the Codes and DataSet based charts, can be saved in external files. This enables you to reproduce those charts instantly.
A detailed overview of those types and locations can be found in the INTERACT Help 
in the topicINTERACT file storage structure.
Note: Your collected observational data is stored in the *.xiact files only!