Average position
Average position is the mean rank of a page for a query, computed across all its impressions. It is a trend indicator, to be read alongside its limits: personalization, location, and sampling cause it to fluctuate.
In practice
A mean of 8 can hide a rank of 3 in London and 15 in Manchester. Rigorous tracking fixes the conditions: country, language, device, and measures the same queries under the same conditions over time. The three-month direction matters more than any single-day figure.