Subgenres of Action-Adventure games:

Subgenres

Although action-adventure games are diverse and difficult to classify, there are some distinct sub-genres. Popular sub-genres include:

• First-person action-adventure, which make use of first-person shooter gameplay, forgoing constant action in favor of important adventure game elements such as environmental problem-solving and a complex plot. These are sometimes called Real-Time Adventure games or RTAs for short. A notable example of this is Metroid Prime and System Shock.
• Third-person action-adventure, in which gameplay is in the third-person. Notable examples include games like Tomb Raider series, The Legend of Zelda series, Rune, Severance: Blade of Darkness, Grand Theft Auto series, and Hitman series.
• Isometric platform games, which feature freely explorable environments with three-dimensional gameplay and two-dimensional graphics using an isometric projection.
• Sandbox, which focus on nonlinear gameplay in an open world. Notable examples include Assassin's Creed and the Grand Theft Auto series.
• Platform-adventure games, which emphasize both exploration and puzzle solving, but also feature traditional platform game conventions. Examples of games of this type are Tomb Raider series, Banjo-Kazooie the Metroidvania games.
• Stealth games, which emphasize avoiding detection by enemies rather than engaging them in direct combat, leading to a greater emphasis on exploration and puzzle-solving than other types of action games.
• Survival horror games, which emphasize "inventory management" and making sure the player has enough ammunition and recovery items to "survive" the horror setting. Survival-horror is a thematic genre with diverse gameplay, however, so not all survival horror games share these features. The Resident Evil franchise popularized this sub-genre and stands to date as the most popular franchise of its kind.

That pretty much confirms what everyone has been telling you.

"make use of first-person shooter gameplay, forgoing constant action in favor of important adventure game elements such as environmental problem-solving and a complex plot."

Basically an FPS focuses on constant action while a FPA focuses more on the story/problem solving.

It's a subgenre of Action-Adventure. Some focus on stories more others are more action oriented.

People say shooters like, Halo is like Contra. Press start and play.