Games development comes in many discipline ranging from a typical head of game project to the game testing interns; with more wacky roles being created as we speak. It would be impossible to grasp games development without first fundamentally understanding what a game is and it's architectural structure.
For this we can look at the individual contents of multimedia. In a typical video game you have audio and visuals in which both are contents of multimedia. But this also puts televisions and internet cat videos into the same category.
By now you would be familiar that digital games are an interactive medium. There must always be an input of instructions to the game and with it a feedback loop, either in the form of visuals, audio or sensory output such as the rumbling of a game controller.
All games are a sequence of challenges to be conquered; puzzles to be solved. A game would be lacklustre if it just involved clicking or wandering around moving visuals with little purposes. But by no means these are not considered games nor entails it has no play values; just in a difficult spot for people to recognise them as games.
A game sets up a stage for players to interact with and introduces it's play as one progresses. This allows players to have unique experiences crafted by the game creator(s).
Amidst the challenges in a game, the multimedia contents play a role in differentiating between poor and mastery works. This is where a game shows it's prowess of quality and design skills; under the umbrella of audio and visuals, these are the works and placement of musics, ambient, sound effects, visual cues, user interfaces, accessibility, etc.