The Trader is a mysterious character who visits your island every week in a large red submarine.
She arrives at midnight GMT on Thursday night and leaves at the same time on Sunday night. There can be extra or longer Trader arrivals at certain instances.
She offers Trader Crates as well as some other offers.
Trader Tickets are obtained in three ways: collecting a Daily Reward, collecting a Supply Chest or buying more from the Trader's extra offers (if available). The former two options yield 1 Trader Ticket regardless of your Rank.
Trader Tickets are also obtained from Warships season rewards. It depends on your rank in Warships.
Trader Tickets are used for obtaining Trader Crates.
Trader Crates are obtained using Trader Tickets. The first Trader Crate per week is free but subsequent Trader Crates will cost you 3 Trader Tickets each.