A parallel gateway is used to represent two concurrent tasks in a business flow. For example, when you receive a payment from a customer you should send their goods to them. These tasks run in parallel.

Based on the condition, an exclusive gateway breaks the flow into two or more mutually exclusive paths. For example, you need to get to an event you would need to determine the distance to travel and then figure the mode of transport to get there.

Breaks the process path into one or more flows. The different paths are triggered by different the scenario at hand. For example, when processing a payment, for different amounts, you need different approvals to take place. This is represented in an inclusive gateway.

Complex gateways are used for splitting or merging complicated process flow scenario. Complex gateways are not often used since simpler gateways are able to be used.