Rank over Partition

RANK ( ) OVER ( [ partition_by_clause ] order_by_clause )

From https://docs.microsoft.com/en-us/sql/t-sql/functions/rank-transact-sql?view=sql-server-ver15

Example:

RANK() OVER (PARTITION BY PersonID ORDER BY createdDate DESC) AS 'Rank'

Partition records based on personID this means for each personID each record set will be grouped by that then operated on as groupings.

Order by createdDate date means that for each personID group starting at 1 each record will be ranked in descending order based on the createdDate