This may come as surprise but even if you've never heard the term, you've likely engaged in some form of adventure travel. That kayaking shore excursion you took on your cruise to Alaska? That counts. The cooking class you took the last time you were in Paris? Yep, that's considered adventure travel, too. According to Shannon Stowell, president of the Adventure Travel Trade Association, adventure travel encompasses three distinct themes: nature, culture and activity. "Basically, it's about getting out of your comfort zone," Stowell explained. While bungee jumping, caving and mountaineering certainly fall under the adventure travel umbrella, these extreme experiences don't solely define this billion dollar sector of the travel industry.To better understand what adventure travel is and why this market has increased at a 65 percent annual rate since 2009, U.S. News talked with Stowell and Christian Wolters, deputy general manager for Intrepid Travel, an adventure travel company that specializes in small group tours. Along with an introduction to this segment of the travel industry, Stowell and Wolters also shared tips on how to incorporate some adventure into your next vacation.See: Best Adventure Vacations in the USAIt may seem like a straightforward concept, but adventure travel is quite variable, according to Stowell. "There's this old image of [adventure travel] being a 20-day trip where you're risking life and limb, and for some people that's still the case, but it's actually much broader," Stowell said. "It's for anyone who is looking for a real-life experience," Wolters explained. "You're not looking at a destination through a tour bus window. You're having a more memorable experience." This can involve anything from a sailing adventure on the Amalfi Coast to a traditional Hutong cooking class in Beijing.According to Stowell, the industry used to divide adventure travel into two core groups: soft adventure and hard adventure. As Stowell put it, this definition was like a light switch with only two, unambiguous options. Now that adventure travel has expanded to include basically any travel experience that draws an individual outside his or her comfort zone, the definition operates more like a dimmer or a dial, with varying intensities of adventure. To better understand where U.S. travelers were on the scale, the ATTA conducted a survey in 2014 polling 1,700 travelers. The results found 24 percent of travelers are "adventure grazers," or first-timers that are willing to accept moderate risk. Meanwhile, 20 percent of travelers identified themselves as "adventurers," or thrill-seekers that repeatedly participate in their favorite adventure activity. "Adventure enthusiasts," or those skilled at their preferred adventure activity, comprised the smallest group at 8 percent. What this illustrated was that adventure travel is not a clear-cut label with one classification for one group of globe-trotters. It's more inclusive and accessible to just about any traveler.See: 10 Best Places to Hike in North AmericaAccording to the ATTA, consumers spent more than $345 billion on adventure travel in 2012. For those just getting introduced to the idea of adventure travel, this may come as a surprise, but Stowell and Wolters said it's mainly a reflection of our current culture. "The travel market is more sophisticated than it used to be," Stowell said. "The experienced traveler is uninspired by a packaged product." As Wolters described it, in the past, if we wanted access to adventure travel we would most likely page through National Geographic or watch a travel show on TV. But now, with the prevalence of social media, we're scrolling through Instagram feeds and seeing that this type of experiential travel is within reach, especially with the influx of adventure travel suppliers.Another reason it may be gaining traction? Adventure travel is often tied to responsible tourism, or travel that diminishes negative economic, environmental and social impacts on a specific destination. Since the core of adventure travel centers on providing memorable and authentic experiences, tour operators depend on the environment and the people who call these destinations home to preserve each destination's identity. And in a world where being green is king, this approach to sustainability only enhances adventure travel's popularity. "The sophisticated traveler wants to know their vacation makes a difference," Stowell said. "People can feel like their tourism dollars are going somewhere and benefiting the destination."If you're intrigued by the idea of adventure travel, incorporating it into your next vacation is actually pretty easy. Stowell and Wolters both suggested examining your interests and picking an activity that challenges you to engage with a destination in a new way. If you enjoy cycling, maybe that means signing up for a half-day biking tour. Or if cooking is your passion, consider enrolling in a class that showcases a destination's distinct flavors. "You can find these experiences right outside your all-inclusive resort," Stowell said. If you're not sure where to begin, Wolters recommended looking at guide books and taking to social media to find bloggers who resonate with you and are stationed in the destinations you're visiting. According to Wolters, they can offer a local perspective that so often defines an adventure travel trip.And if you'd like a little more guidance, consider booking through a group tour company like Journeys International, KE Adventure Travel or Intrepid Travel — these companies offer a variety of themed trips to destinations across the globe and connect travelers with local guides who act as their destination ambassadors. These guides are especially helpful if you're traveling to a destination where you don't speak the language. To further narrow down your search, both Intrepid and Journeys International also detail the physical and cultural rating for each itinerary. For instance, a trip to Egypt might be labeled with a culture shock rating of three, while a journey through western Canada may only receive a one on the culture shock scale. KE Adventures offers a similar distinction for each of its trips with a "holiday grade," ranging from one to 12, which details the physical fitness and skill level required for each trip.Whether you're a grazer or an enthusiast, Stowell recommended approaching adventure travel with an open mind, and preparing for "moments of awe."See: 6 Volunteer Vacations to ExperienceAbout the author: Ann Rivall is a Travel Editor at U.S. News. You can follow her on Twitter, circle her on Google+ or email her at email@example.com.