The Nstein TME is a text mining engine that is usually bundled with WCM. The TME is used to generate taxonomies and metadata using specialized modules.
This action will refresh all of the semantic information associated with your content. This includes IPTC categorization, concepts, entities (Organizations, people and places), tone and summaries. This process can take a long time depending on the amount of content to refresh.
If you want to keep existing information, make sure to check Merge semantic data.