When an AI answer recommends several brands, where do you land? Average Rank is your mean position across the prompts where you're mentioned, and lower is better. An average near 1 means you're consistently the top pick; an average around 6 means you usually sit mid-list.
It completes the picture that Top-Ranked % starts. Top-Ranked % is the binary "how often am I #1"; average rank captures the whole distribution. A brand that's rarely first but reliably 2nd-3rd has a strong average rank and a modest Top-Ranked %, a very different position from one that's occasionally #1 and otherwise nowhere near the top.
Because it only counts prompts where you appear at all, read it next to Share of Voice: a great rank across few mentions is a narrower win than a solid rank across many.