When replicated data needs to be updated at the Subscribers, you can use snapshot replication or transactional replication with updatable subscription options or you can use merge replication. The method you choose depends on your replication topology and the needs of your application and its users.
Use merge replication when . . .
Use snapshot replication or transactional replication with immediate updating or queued updating when . . .
Replicated data is read and updated at the Subscriber.
Subscriber and Publisher are only occasionally connected.
Conflicts caused by multiple updates to the same data are handled and resolved.
You need updates to be propagated on a row-by-row basis, and conflicts to be evaluated and resolved at the row level.
Replicated data is mostly read-only at the Subscriber.
Subscriber, Distributor, and Publisher are connected most of the time, but this is not necessary for queued updating subscriptions.
Conflicts caused by multiple updates to the same data are infrequent.
You need updates to be propagated on a transaction basis, and conflicts to be evaluated and resolved on a transaction basis (the entire transaction is either committed or rolled back).