About Gateways
Gateways split and join data paths in a process flow. No service is associated with a gateway step, and other than determining direction of flow, they have no effect on the process data going through the gateway. Use a gateway only when you need to merge or split a data flow.
A single gateway can have multiple inputs and multiple outputs flows, and can be configured to perform both a merge (or join) and a split in a single step. However, BPMN best practices recommend that you configure any single gateway to perform only one of these functions. In this case, you would create two sequential gateways, the first one to merge and the second one to split the data flow.
There are four different gateway types, as described in
About Gateway Types. For detailed information about gateway behavior, see the BPMN 2.0 specification at
http://www.omg.org/spec/BPMN/2.0.
Parallel and complex gateways support join timeouts, inclusive and exclusive gateways do not support join timeouts. As of version 9.7, Parallel gateway steps support timeout and unsatisfied join transitions. Exclusive gateway does not have timeout or unsatisfied join transition conditions.