A queue allows you to defer the processing of tasks like sending e-mails or firing API requests until you’re ready to deal with them. In practice, you can queue anything you like; but it’s primarily designed for anything that would either bring your server to a crawl if you were to do all processing at once or where rate-limiting would otherwise take effect.

https://medium.com/@bastones/a-simple-guide-to-queuing-mail-in-laravel-f4ff94cdaa59