> ## Documentation Index
> Fetch the complete documentation index at: https://docs.spaceport.xyz/llms.txt
> Use this file to discover all available pages before exploring further.

# Key Entities

> Understanding the core entities in the Spaceport ecosystem.

The Spaceport ecosystem revolves around a few key entities. Understanding these will make the SDK's structure intuitive.

* **User**: Represents an actor in the system, either a **Licensor** (who owns assets) or a **Licensee** (who wants to use assets). Every user has a unique ID that acts as their identifier.
* **Asset**: The digital "thing" you want to license. This could be a 2D image, a 3D model, a piece of music, or any other digital file. When an asset is used in a listing, it becomes a unique, verifiable digital object.
* **Smart License**: A reusable template for a license agreement. It defines the rules, terms, and conditions under which an asset can be used. Think of it as a dynamic, programmable contract form.
* **Listing**: An offer to license an Asset to others. It combines an Asset with a Smart License and sets a price and other commercial terms. This is what a Licensee sees and agrees to.
* **Agreement**: The legally and cryptographically binding contract that is created when a Licensee accepts a Listing.
* **Product**: A commercial item created by a Licensee that uses a licensed Asset. For example, a video game that includes a licensed 3D model. Products are used to track usage for royalty reporting.
* **Royalty & Invoice**: The system for tracking and paying for the use of an asset. Licensees report their sales data (via Invoices), and the system automatically calculates the royalties owed to the Licensor.