For each primary database managed by a Replication Server, there is a distributor (DIST) thread, which in turn uses SQT to read from the inbound queue and SQM threads to write transactions to the outbound queue.
Thus, for example, if there are three primary databases, then there are three inbound queues, three DIST threads, and three SQT threads.
In determining the destination of each transaction row, the DIST thread makes calls to the following modules: Subscription Resolution Engine (SRE), Transaction Delivery, and Message Delivery. All DIST threads share these modules.