This section describes the important concepts for the Simple Queue Service (SQS)
A queue is a named destination for messages in an account. A queue has a URL that uniquely identifies it on the cloud.
When a message is delivered to a client it is hidden from other clients for a period to prevent duplicate handling. If the message is not handled by the first client it will later become visible for handling by other clients.
A dead-letter queue can be used for undeliverable messages. Using a dead-letter queue allows for handling of messages that would otherwise not be processed.
A delay queue allows messages to be available from a queue after a delay period rather than as soon as messages are sent to the queue.
Short or long polling can be used when receiving messages. For short polling there is an immediate response whether a message is available or not. For long polling a delay of up to 20 seconds is used and the response will occur when a message is available or when the given timeout is reached even if there is no message.