Structured search is about interrogating data that has inherent structure. Dates, times, and numbers are all structured: they have a precise format that you can perform logical operations on. Common operations include comparing ranges of numbers or dates, or determining which of two values is larger.
Text can be structured too. A box of crayons has a discrete set of colors:
red, green, blue. A blog post may be tagged with keywords
distributed and search. Products in an ecommerce store have Universal
Product Codes (UPCs) or some other identifier that requires strict and
structured formatting.
With structured search, the answer to your question is always a yes or no; something either belongs in the set or it does not. Structured search does not worry about document relevance or scoring; it simply includes or excludes documents.
This should make sense logically. A number can’t be more in a range than any other number that falls in the same range. It is either in the range—or it isn’t. Similarly, for structured text, a value is either equal or it isn’t. There is no concept of more similar.