[問題] EC2 裡面的 persistent request 的意思

如提，我在 EC2 設定裡面看到這個選項：persistent request
閱讀解釋之後還是不太懂：

Persistent Requests: Spot Instance requests can be one-time or persistent. A one-time request will only be satisfied once; a persistent request will remain in consideration after each instance termination. This means that with a persistent request, after your request has been satisfied and your instance has been terminated—by you or by Amazon EC2—your request will be submitted again automatically with the same parameters as your initial request. A persistent request will continue submitting the request until you cancel it. A persistent request is useful when you have a large amount of computing that you want to get done but only below a certain price. By using a persistent request, you can launch instances any time the Spot Price is below your maximum price and steadily work through your task.

我可以翻譯整個段落，像是「單次請求可以被滿足一次」，但什麼是「請求」，什麼是「滿足」，裡面沒有諸多定義與解釋，所以雖然讀完了，仍然不清楚意義何在，希望有人可以舉個例子。