-What is cosine similarity? is a metric to compare two vectors depending on the inner angle, and that way, it’s not affected for the size of the vector
Cosine of two vectors is: $$cos(Beta) = \frac {\vec(v) * \vec(w)} {|\vec(v)| * |\vec{w}|} $$
if the angle is orthogonal, the cos of 90 is 0, meaning if the cosine similarity is 0, means that the vectors are orthogonal, meaning that the similarity is 0.