An adventure is something exciting that happens to someone. An adventure can be a made-up story, or it can be something that happens in real life.
People often like to read stories about a person or a group of people who go off and have an adventure. There is often some danger in the story. Enid Blyton wrote stories about The Famous Five who go off to have exciting adventures. Harry Potter has lots of adventures: he meets strange people and gets into lots of dangerous situations.
People in real life like to have adventures. They may be explorers who like to go to far-away places where no one has ever been before.
An adventure playground is a playground for children where they can climb, swing and jump on things. They have been made by adults for children to use and are normally quite safe.
An adventurer is someone who spends all his life going on adventures or doing things that are risky.
An adventure game is a video game about adventures.
The word venture is a short form of "adventure". A "business venture" is a business project in which there is a lot of risk. "Venture" can also be a verb: "They ventured out into the storm".