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. 
yes you can definitely say that. the definiton of a backpacker evolves as travellers from different cultures and regions participate so many people will call it something different but it definitely involves traveling with a backpack. some hiking can definitely be called backpacking