Redruth, or Tom Redruth, to give him his full name, is one of Squire Trelawney's loyal and faithful servants. He is so loyal and faithful, in fact, that the Squire takes him on his voyage to Treasure Island along with two more of his servants, Joyce and Hunter.
Tom's a fairly minor character in the story. He doesn't have much to do, and there's nothing in the way of character development. In fact, he's a pretty flat character who doesn't really change throughout the book.
Even so, Tom's death provides us with one of the most emotional scenes in Treasure Island. Tom, along with Joyce, Hunter, and the other men, had just been involved in an intense exchange of fire with some pirates. At first, all seemed well; one of the pirates was killed, and the others ran off. But while the men were rejoicing, Tom was suddenly struck down by a bullet.
Despite Doctor Livesey's best efforts, there's nothing that can be done for him, and Tom passes away. The normally cool, calm, and collected Squire is absolutely devastated by the death of his faithful retainer and cries like a baby. This gives us a clear indication of just how much poor Tom meant to him.