Action-adventure game

An action-adventure game is a video game that combines elements of the adventure game genre with various action game elements. It is perhaps the broadest and most diverse genre in gaming, and can include many games which might better be categorized under narrow genres. The first known game in this genre is the Atari 2600 game Adventure (1979).
With the decline of the adventure game genre from mainstream popularity, the use of the term (and the hybrid term "action-adventure") has been more liberal. It is not uncommon for gamers to apply the term "adventure" or "action adventure" to describe the genre of fiction to which a game belongs, and not the gameplay itself, usually to the dismay of adventure game purists.
It is important to note the distinction between thematic genres and gameplay genres, as in this case they have very different meanings and etymology. "Adventure" is a reference to the early computer game of the same name, and has no thematic or narrative meaning, nor any connection to adventure movies. Similarly, while action games usually do have violent themes similar to action movies, this is not a requirement.
Action-Adventure is a hybrid genre, and thus the definition is very inclusive, leading it to be perhaps the broadest genre of computer and video games.

Typically:
Pure adventure games have situational problems for the player to solve, with very little or no action. If there is action, it is generally confined to isolated mini-games.
Pure action games have gameplay based on real-time interactions that challenge the reflexes.
Action-adventure games engage both reflexes and problem-solving, in both violent and non-violent situations.

Definition and confusion
The term action adventure itself has become more generalized since its introduction, and can now be used to refer to virtually any game which combines elements of real-time action-based challenges with some element of problem-solving. The genre exists largely to distinguish these games from pure adventure games, or from role playing games. It should be noted that adventure games never have a pronounced action element, limiting the action-based challenges to mini-games or other brief sequences. RPGs by definition have elements of pen and paper role playing games, such as "experience points" and other statistic-driven gameplay. Games in the Metroid series are better classified as action-adventure because of this.
Due to the lack of a definition of the term "action-adventure" (although it may be considered a game that contains elements of both genres on assumption) there are quite a few disagreements in the community and in the media over what actually constitutes an action-adventure game. One definition of the term "action adventure" may be '“An action/adventure game is a game that has enough action in it not to be called an adventure game, but not enough action to be called an action game.”' Others see action games as a pure genre, while an action-adventure is an action game that includes situational problem-solving. Regardless, disagreements over which games fit under the categories are particularly prominent in articles over the internet and media. Action-adventure games may have a free roaming feel, but the term is usually not used when a narrower sub-genre, like Action-RPG is better applied.

Common features
In action-adventure games, while reflex-based actions are required (often revolving around combat or the avoidance thereof), the gameplay still follows a number of adventure game genre tropes (gathering items, exploration of and interaction with one's environment, often including an overworld connecting areas of importance, and puzzle-solving). While the controls are arcade-style (character movement, few action commands) there is an ultimate goal beyond a high score. This type of game is often quite similar to computer role-playing games.
They are distinct from graphic adventures, which sometimes have free-moving central characters, but also wider variety of commands and fewer or no arcade game elements and are distinct too from text adventures, characterized by many different commands introduced by the user via a complex text parser and no free-moving character. While they share general gameplay dynamics, action-adventures vary widely in the design of their viewpoints, including bird's eye, side scrolling, first-person, third person, over the shoulder, or even 3/4 view.
Many action-adventure games simulate a conversation through a conversation tree. When the player encounters a non-player character, they are allowed to select a choice of what to say. The NPC gives a scripted response to the player, and the game offers the player several new ways to respond.