Update ReadMe.md

update README.md

README.md

@@ -61,6 +61,16 @@ When a user submits a query, the system enforces groundedness through a multi-l
    of the cited chunks. The similarity is calibrated to a 0–1 scale and averaged, producing a single
    groundedness score that is surfaced to the user with a visual indicator (green/yellow/red).
 
+## Similarity Metrics for Semantic Understanding
+
+Cosine similarity measures how closely two vectors (representing data like words, images, or preferences) are aligned in a multi-dimensional space by calculating the cosine of the angle between them.
+
+Archetypical cosine scores range from -1 to 1. 
+
+1: Vectors point in the exact same direction (highly similar).
+0: Vectors are at a 90-degree angle (orthogonal/unrelated).
+-1: Vectors point in opposite directions.
+
 ## Design
 
 Two-package monorepo: