Record merge
Combining duplicate records into one, keeping the history, associations and best values of each.
A merge keeps one record as primary and folds the others into it. In HubSpot, the primary record's property values win, empty properties take the secondary record's values, and associations and timeline activities of both records end up on the merged one.
HubSpot merges can't be undone, so each merge deserves a check first: is it really the same person or company, and is the right record kept as primary?