I love going hiking, which is what I prefer to call it.  Other countries have all sorts of terms for it like bushwalking, which is what Australians call it. 
Yes, I have heard that term.  I think that the British have some slang terms for it, too.  I like hiking, as well.
Yes, it's a popular activity no matter where you go in the world, not to mention all the health benefits of a good walk.
Definitely is good for the heart, soul, and body.  We hike up some small mountain trails in my local area.  It's a great family activity.
Well if you like a good trail, try out the Appalachian National Scenic Trail.  It's about 2,200 miles long give or take a few with changes over the years.
I have walked portions of the Appalachian Trail.  I haven't done the whole thing, because I don't have months to spend on it, lol.
Well you could also try the Florida National Scenic Trail, it runs through the Big Cypress National Preserve, great scenery.