The CRM finds likely pairs with the same email, the same phone or the same full name. Merging keeps one record: every note, text, email, call, task, deal and appointment moves to it, missing details fill in from the other, and the other record points to the one you kept from then on. Pairs you mark as not duplicates, and people you linked (a couple sharing a phone), are left out.
Open the duplicates list
On People, open the duplicates view from the list menu, or open a person and look for the duplicate notice.
Compare the two
Check the two records side by side and pick which one to keep.
Merge
Press Merge. If they are really two people, mark them as not duplicates instead and they won’t be suggested again.