That means that you have to install the mod and fill out the form to join the server if you need any more information, I highly suggest you join the Discord:
The Minecraft servers are looking for dedicated players who will participate in their gaming community. Minecraft servers are completely free to play. Join today and play the best Minecraft servers in of the most popular games in the world! Players can join the server in a few different ways. First, you can download the Minecraft launcher, find the server and join with just a few clicks of your mouse. If you want to become a regular user of the Minecraft server, you can also apply to become a member of the community and make your presence known.
A Minecraft server (Java/Bedrock) is a server program that allows players to play the game of Minecraft. In this list you will find hundreds of online servers running the game of Minecraft. These servers offer players a safe place to play the game and have fun together. There are servers for just about any kind of game you can think of. This list contains many different types of servers.
Survival is the most popular server type for Minecraft to play. You can find a lot of mods for it, and its population is really high. Minecraft survival server is based on a more realistic Minecraft, and players here get to play on a world that has a lot of possibilities for how the game will play out. You can play on these servers with friends, and with the same server and its features, your session is going to be more or less unique. In addition, it is more complicated than the other Minecraft servers, and to play you are going to have to become familiar with the game.