What did the internet term transmigration mean?

Time travel was a fantasy or sci-fi concept of going back to the past or into the future. In online parlance, transmigration usually referred to the experience of transmigrating to a novel, anime, game, or other fictional world to become a character. Time travel is often used as a plot design to let readers feel the excitement and adventure of time travel, while also strengthening the emotional conflict and plot development of the story. Time travel could also be used as the theme of a role-playing game to let players experience the feeling of time travel in the game.