Appstream is a metadata standard for your software releases which gets used by package managers and app stores as well as web sites such as kde.org (one day at least).
If you are incharge of making releases of an application from KDE mind and make sure it has an appstream appdata file. You should also include a screenshot preferably in the product-screenshots git repo.
You should also add release data to your appstream files. See the docs for the full details. Not all the data will be very practical to add before the release time but it is useful to at least have a version number and maybe a release date added in.
I’ve added this to the Releasing Software wiki page now. And I’ve written a wee script appstream-metainfo-release-update to update the XML with a simple command which I’ve now added to the Plasma release process.