This is a new feature we have added to assist in getting more focused blog posts for a specific product.
By specifying a keyword - we do up-front filtering on blog posts before checking them any further. If they dont contain the keyword they are ignored.
For example:
Adding the keyword Recipe means blog posts must have one or the following present
Title word match
Tag match
As a dynamic filter - this option may also be linked to a metafield attached to the product.
Leaving blank will ensure no filters are applied