Asset packs, or asset packages, are collections of Struckd assets that can be used in the app to create games. These assets can include 3D characters, animals, weapons, explosives, buildings, environmental elements, and much more.
Free assets are available in the assets library at all times. However, you can also see assets with a package icon - those assets are part of the premium assets library.
The pro assets pack is available with a weekly or monthly subscription. Some assets can be obtained via Struckd coins. Here is a list of all premium asset packs available in the Struckd app.