What they contain
Ground texture and road collections are texture-focused libraries. They expose texture assets with names, previews, and storage metadata so the Editor and mapping rules can reference consistent surfaces instead of embedding texture choices directly into each project.
Vector mapping rules can point at texture assets through textureAssetId. That lets a rule such as a grassland, forest, road, or sand rule classify the feature and also provide the texture that should represent it during editing or export.
How they are used
The Collections page previews texture collections as item lists. In the custom vector mapping builder, a rule can choose a texture asset when the collection data exposes one.
When a custom vector mapping rule has no texture asset, the backend tries to find a built-in or default vector mapping rule with the same source name and reuse its texture reference. This keeps common cloned mappings useful even when you only edit names, layers, categories, tags, or priority.
Custom texture collections
The platform model supports texture collections as first-class collection records, but the current dashboard custom-collection dialog does not create new ground texture or road collections. User-created collections in the visible workflow are currently FS25 vector mapping collections.
Texture libraries are imported and maintained through the collection content upload paths, then consumed by mappings, editor presentation, and export generation.