Replication Types

Here are the replication types available in SQL Server 2012:

Snapshot
Creates a complete copy of the data - is useful for keeping a copy of the database for reporting from.
Snapshot replication is suitable where the data doesn't change often, most of the changes occur over a short period or only a small amount of data needs to be replicated.

Transactional
Subscriber databases are kept up to date with changes to the publishing database.
Transactional replication is suitable where the subscribers need updates as they occur.  It is suitable for situations where changes to data are need by subscribers very soon after they occur, the publisher is not a SQL Server 2012 instance (eg it is an Oracle database) or changes must be applied to the subscriber in the same order in which they occurred.

Peer-to-Peer
Allows updates by peers to be propagated to other nodes in the replication topology so they are all kept updated with each others changes.  You must partition the data to prevent conflicts so that the same row will not be updated at separate locations. If a conflict occurs the replication will fail.

Merge
For mobile and distributed server applications where data conflicts are possible.  The publisher and subscribers track changes made by using triggers. When a subscriber synchronizes with the publisher, they exchange all rows that have changed since the last synchronization.