- The player knows they are making a choice
- The choice has consequences
- The player has information to inform their choice
As a corollary to the second requirement ("choices have consequences"), there must necessarily be multiple options for the player that have different outcomes. Although players must have information to inform their choice, this does not mean that the GM must provide a comprehensive list of options and their consequences before the choice is made.
Meaningful choices give the players agency, and increase their engagement with the game. Meaningful choices do not need to be hard choices, although hard choices are often more memorable and revealing of a player character's personality.
For instance, if a player can choose whether their superhero decides to let the supervillain escape with their hostage, or attempt a risky takedown, that is a meaningful choice. On the other hand, if players purchase equipment for their characters, but in the next session they are captured and end up with only the equipment they were able to steal during their escape, their equipment purchases were not meaningful choices.
Railroading is a stereotypical case of a GM failing to offer meaningful choices to their players.