ON CONFLICT triggers are intended for the destination tables involved in replication in order to manage replication conflicts. For example, if you have an ON CONFLICT trigger on the destination customer table, and the source table record being replicated does not match the record at the destination, your ON CONFLICT trigger can take steps to handle the conflict.
By default, conflicts are ignored and the conflicting destination table record will be replaced by the source record. However, by creating an ON CONFLICT trigger, your code can choose instead to keep the destination record, or your code can write the source record to a special table designed to holds conflicts until an administrator can evaluate the conflicting values manually.
Replication and ON CONFLICT triggers are discussed in greater detail in Chapter 10.