Advanced Search within Documentation
The search bar is used to find information across product documentation, knowledge base articles, frequently asked questions, support notes, release updates, articles and more.
Within Help Portal (Documentation), the search bar offers an Advanced Search for partial, full, or exact searches across user guides.

Quotation Marks (") can be used around text for an exact match search which is beneficial when looking for specific error message text or guide names.
Filtering Results by Content Types
The Help Center Search offers filters after executing a search, including Type. The icon on the right side of the result indicates the type, and the results can be refined in the menu on the left, or by Date and Relevance drop-down field in the top-right.

For an understanding on how to search for documentation within the Help Center, watch this video.