Basically, when you export a .ted, you are only exporting your team/players info, not the kits/image files themselves. However, it does store the name of those files, so if you put those image files in your WEPES folder and keep them with the same name as when you imported them into the team, when you or someone else import the .ted file it will also fetch those images from the WEPES folder and apply them to your team.
For example, if you have a team with the files:
You export the .ted file, it's stored in your USB flash drive. If you want to share with others, you share the .ted file and also the image files TeamLogo.png, TeamHomeKit.png, etc. So when you put all those in your WEPES folder it will import the team/player data from the .ted and also apply the kits. If you change the file names or delete those kits from the WEPES folder, importing the .ted won't import those image files.
So, in short, the .ted file does not store the images themselves, but rather the association between that team and the image files. You need to keep the images with the same file name alongside the .ted file in your WEPES folder for the import to work properly with all images