Explanation
ReceiveMode enumerates the values for the receive mode. The default is PeekLock.
Fields:
PeekLock: Specifies the PeekLock receive mode. This is the default value for ReceiveMode.
ReceiveAndDelete: Specifies the ReceiveAndDelete receive mode.
Note: You can specify two different modes in which Service Bus receives messages.
Receive and delete. In this mode, when Service Bus receives the request from the consumer, it marks the message as being consumed and returns it to the consumer application.
Peek lock.
Reference:
https://docs.microsoft.com/en-us/azure/service-bus-messaging/service-bus-queues-topics-subscriptions
https://docs.microsoft.com/en-us/dotnet/api/microsoft.servicebus.messaging.receivemode