A proxy sits in front of your other servers and gives them all one address. Players connect to the proxy, and it forwards them to whichever server you choose, so they can move between servers without disconnecting. A proxy does not run a world of its own, so you need at least one regular server behind it.
Buy a proxy from us and it arrives configured. Adding a server behind it is a drag-and-drop in your dashboard, with no config files to edit.
Order two or more servers at once and our entry proxy comes free with them, a larger one paying only the difference.
You are free to run your own proxy too. Buy a regular server and put any proxy in front of it, hosted with us or somewhere else.
Currently Aquila-managed proxies are only available for Minecraft servers.
Why you might want to use a proxy:
Note that restarting the proxy itself does drop connections, forcing players to reconnect.