Basically two or more users are trying to update the same record in the same database (through merge replication)…and the changes are not being saved after a synchronization. They are, however able to update different records and the changes are saved after synchronization.
This is because of merge replication conflicts, conflicts happen when a same row\column is updated from different sites. If your conflict resolution is not "interactive" SQL Server will handle the conflicts automatically and the winner row is updated across all servers and the loosing rows are written into conflict table conflict___. You can view these information in conflict viewer also. [KB article] about conflict. :