Key components of games are goals, rules, challenge, and interaction. Games generally involve mental or physical stimulation, and often both. Many games help develop practical skills, serve as a form of exercise, or otherwise perform an educational, simulational, or psychological role. According to Chris Crawford, the requirement for player interaction puts activities such as jigsaw puzzles and solitaire "games" into the category of puzzles rather than games.

Attested as early as 2600 BC, games are a universal part of human experience and present in all cultures. The Royal Game of Ur, Senet, and Mancala are some of the oldest known games.

Ludwig Wittgenstein was probably the first academic philosopher to address the definition of the word game. In his Philosophical Investigations, Wittgenstein demonstrated that the elements of games, such as play, rules, and competition, all fail to adequately define what games are. Wittgenstein concluded that people apply the term game to a range of disparate human activities that bear to one another only what one might call family resemblances.

French sociologist Roger Caillois, in his book Les jeux et les hommes (Games and Men), defined a game as an activity that must have the following characteristics:

Computer game designer Chris Crawford attempted to define the term game using a series of dichotomies:

Crawford's definition may thus be rendered as: an interactive, goal-oriented activity, with active agents to play against, in which players (including active agents) can interfere with each other.

Games can be characterized by "what the player does." This is often referred to as gameplay. Major key elements identified in this context are tools and rules that define the overall context of game and that in turn produce skill, strategy, and chance.[clarification needed]

Games are often classified by the components required to play them (e.g. miniatures, a ball, cards, a board and pieces, or a computer). In places where the use of leather is well established, the ball has been a popular game piece throughout recorded history, resulting in a worldwide popularity of ball games such as rugby, basketball, football, cricket, tennis, and volleyball. Other tools are more idiosyncratic to a certain region. Many countries in Europe, for instance, have unique standard decks of playing cards. Other games such as chess may be traced primarily through the development and evolution of its game pieces.

Many game tools are tokens, meant to represent other things. A token may be a pawn on a board, play money, or an intangible item such as a point scored.

Games such as hide-and-seek or tag do not utilise any obvious tool; rather, their interactivity is defined by the environment. Games with the same or similar rules may have different gameplay if the environment is altered. For example, hide-and-seek in a school building differs from the same game in a park; an auto race can be radically different depending on the track or street course, even with the same cars.