Players make things happen by using their wits, their Player Characters (PCs)' skills, equipment, abilities, and their decisions, which they then play out in character; just like how actors playing their characters make things happen in a movie or a TV show. However, the difference between a movie and the events of a RPG, are that players retain control of their characters and are the ones to make things happen. Sometimes, according to the GM's plans, and sometimes, despite them.
If you are familiar with roleplaying, these concepts should already be familiar to you, but if not, the gist of it is this: you play as your character the characters you control would, speaking the words they would say, doing the actions they would do. GMs must be familiar with this concept in order to run a game of MazeWorld, but they can ease people who are new or unskilled at roleplaying with simple interactions, like a discussion or a short scene between a NPC (controlled by the GM) and a newbie player's PC, to gauge these players' abilities and teach them how to play.
The role of the game's rules and mechanics is to help with conflict resolution and problem solving, to introduce elements of chance, randomness and uncertainty, and to determine the outcome of the story, action by action. Will your character aim her [[MP5A3]] at the chest of the bad guy, knowing he has body armor, or will she risk a shot to the head in an attempt to bring him down faster, knowing she might miss? Will this rag work on your wound or will you need to scrape by for a real bandage? Do you have enough supplies to last you until the next town, or is death around the corner?