PostEaseThe short answer
Share of voice measures how much of the total conversation or mentions around a topic, category, or set of keywords a specific brand accounts for, relative to its competitors. It is a comparative metric by definition. A brand's own mention count says little without knowing how it compares to competitors in the same space.
Why it matters as a competitive signal
A brand can have strong engagement on its own posts while still holding a small share of the overall conversation happening in its category. Share of voice reveals that competitive context in a way an account's own internal metrics cannot.
What moves it
Share of voice reflects the total volume of conversation, not only owned content. It responds to being mentioned by other accounts, appearing in relevant conversations beyond a brand's own posts, and word-of-mouth. Posting more from the brand's own account moves it very little.