The terms Transaction Coordinator and Transaction Manager are mostly interchangeable in terms of transactions with JBoss EAP 6. The term Transaction Coordinator is usually used in the context of distributed transactions.
In JTA transactions, The Transaction Manager runs within JBoss EAP 6 and communicates with transaction participants during the two-phase commit protocol.
The Transaction Manager tells transaction participants whether to commit or roll back their data, depending on the outcome of other transaction participants. In this way, it ensures that transactions adhere to the ACID standard.
In JTS transactions, the Transaction Coordinator manages interactions between transaction managers on different servers.