Snapshot replication is used for copying whole objects from a publisher to a subscriber. Although a snapshot can be filtered, snapshot replication has no facility for sending incremental changes to subscribers.
SQL Server implements snapshot replication via the Snapshot and Distribution Agents. The Snapshot Agent handles creating the snapshot, which consists of BCP data files and T-SQL scripts. The Distribution Agent takes the snapshot and applies it to subscribers. All along the way, both agents access and update replication system tables in the distribution database.