Pirates of the Burning Sea has 2 Live Servers:
You can choose to play on either server, but remember: PotBS is an international game, with a lot of players from different countries around the world playing across all of its servers.
The difference between the two servers are the Port Battle (PB) Window. Antiqua is as American server focused on prime-time USA players, while Roberts is as European server focused on prime-time EU players.
That being said, it makes little sense to play on Antiqua for Port Battles (PB) as a player from Europe with a daily job. Most PBs will take place in the night. Likewise, it makes even less sense to play on Roberts as a player from America, the PBs will then take place in the (early) morning.