Hello AJ Jeffers,
Welcome to the Microsoft Q&A forum.
The "Steward" is a person or group responsible for managing the glossary. Here, you need to select a steward from the list of Microsoft Entra users or groups who will manage the glossary
Please follow this tutiroal to create and manage business glossaries:
https://learn.microsoft.com/en-us/purview/how-to-create-manage-glossary
I hope this helps. Please let me knwo if you have any further questions.
I hope this helps.