Traditional TTRPGs have almost always relied on player reactions in order to function. In other words, there is an evil wizard out to take over the world. The player characters are good, therefore its their duty to stop the wizard. Game play then follows a traditional storytelling narrative of protagonists working to return their world back to the status quo.
Bad guy makes a move, good guys move to stop him. They react to the situation the Game Master (GM) presents. This limited style of gameplay can grow tiresome and redundant and places almost the entire burden of game creation on the GM. That's where proactive roleplaying comes in. With proactive roleplaying, GMs give over the narrative to the players. They imbue their characters with goals and desires, wants and needs, and then let them make the decisions about how to achieve those things. Its no longer up to the GM to provide the entertainment. The characters choose what to do to achieve their goals, and the GM is the one reacting to their choices. Every conflict and "adventure" a character goes on is in service to their goal, rather than the typical "random bad guy of the week" adventure. The Game Masters Handbook of Proactive Roleplaying gives GMs and players all of the information they need to play their favorite 5E TTRPG in their favorite settings, while transforming their games from reactive and restrictive to proactive, unbounded, player-driven narratives.
