CAN Bus multidirectional
The point of CAN is that you have (usually) a single controller and a single transceiver in a CAN node (some safety critical systems may have more than one bus for redundancy).

All CAN nodes talk bidirectionally over the same single wire pair.

The number of transmit and recieve buffers (and filters / masks) reduces the load on the firmware. For example if have 8 transmit buffers and you want to send 5 messages that have lower priority than the current bus traffic you can simply load all of them at once and the controller will send them whenever the bus is available. If you have only one buffer, then you can queue just one frame in the controller and the firmware needs to queue the rest.