Without the `mediaproxy` function, Pleroma doesn't store any remote content like pictures, video etc. locally. So every time you open Pleroma, the content is loaded from the source server, from where the post is coming. This can result in slowly loading content or/and increased bandwidth usage on the source server.
With the `mediaproxy` function you can use nginx to cache this content, so users can access it faster, because it's loaded from your server.
If you came here from one of the installation guides, take a look at the example configuration `/installation/pleroma.nginx`, where this part is already included.
* Append the following to your `prod.secret.exs` or `dev.secret.exs` (depends on which mode your instance is running):