I like to hike on my free time.  Have you ever been hiking? 
nope. but in new zealand a hike also referred to as a long vigorous walk is also called tramping!
That's a new term I've never heard before. What kind of shoes would someone wear hiking in your opinion? 
walking shoes if you're mostly walking, running shoes if youre mostly running. you would want the shoe to match the activity you do the most. also hiking is a popular activity worldwide and studies suggest that all gorms of walking, even long hikes have health benefits.
I would guess that hiking is good cardiovascular exercise. Is that accurate? 
yup. your heart rate will definitely build on a hike. and other terms for hiking in the uk are simply walking or rambling, while walking in mountanious areas is called hillwalking
It seems that hiking is popular all over the world.  Do people go from country to country hiking for fun? 
yes my friend will hike in different countries. i'd imagine those in europe willl do the same because they can drive to a new country easily. they probably most often participate in a day hike which is a hike that can be completed in a single day.
It is also called backpacking if I'm not mistaken.
Backpacking (travel)
Backpacking is a form of low-cost, independent travel. It includes the use of  public transport; inexpensive lodging such as youth hostels; often a longer duration of the trip when compared with conventional vacations; and typically an interest in meeting locals as well as seeing sights. Despite the name it does not have to involve travelers carrying belongings in a backpack, although that is a common practice.
The definition of a backpacker has evolved as travelers from different cultures and regions participate in the
the UK, along with rambling (a slightly old-fashioned term), hillwalking, and fell walking (a term mostly used for hillwalking in northern England). The term bushwalking is endemic to Australia, having been adopted by the Sydney Bush Walkers club in 1927. In New Zealand a long, vigorous walk or hike is called tramping. It is a popular activity with numerous worldwide, and studies suggest that all forms of walking have health benefits.
Related terms.
In the United States, Canada, the