Document Understanding : To extract and interpret data from various types of documents, including structured, semi-structured, and unstructured documents.
It uses AI and machine learning to understand the content and context of documents, enabling automation of document-heavy processes
AI Center: To deploy, manage, and monitor machine learning models within the Automation Cloud platform. It provides a centralized environment for data scientists and developers to collaborate on building and deploying AI-powered solutions.
If you want to extract the data from invoice / documents then you will use document understanding
Hope this answers your questions
Thanks,
Srini