The Wayback Machine is a tool found on the Internet Archive for saving and restoring old webpages. Many people save webpages in the Wayback Machine so they can revisit them later. The Wayback Machine is capable of saving a webpage in its current state forever so you can revisit that same webpage at a later date regardless of what changes may have been made to it since then, including if the webpages have been taken down entirely.
Sometimes saving webpages in the Wayback Machine can be slow. Slow saves reduce the number of times people may be willing to save webpages. If you experience slow saves, you ought to check the article 6 different ways to save webpages in the Wayback Machine posted to the Internet Archive blog.