Position zero
Position zero designates the space above the first standard result, occupied by an answer extract. Appearing there captures maximum visibility without technically holding the first ranked position.
In practice
Since AI-generated answers arrived, position zero coexists with AI Overviews, which are replacing it for a growing share of queries. The capture logic remains similar: compact answer, clear structure, sufficient authority. What changes: AI composes its answer from multiple sources, while the classic snippet cited only one.