Nice to meet you! I love to go on hikes. Hiking is what we call going for a long walk on trails in the country. At least that's what we call it in the US and in Canada.
I've always thought about hiking but am unsure where one would go to hike.
You can go hiking on any trail, or even off a trail through the countryside. 
Would walking up mountains or on flat lands constitute a hike. And how long would you have to walk for?
As long as you want. However a "day hike" is a hike that you do in one single day. Some hikes are even longer!
Whats the best hike you've ever taken? And where was it?
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
criticized him, saying they couldn't tell what was happening. Of the call, Fyffe said, "Frankly, in listening to the replay of the call through the years, I've never thought it was my best. I probably did go too crazy, but I think the listener could tell what was going on without any problem. No matter what I think about it, Auburn fans still come up to me and tell me it was the best call they've ever heard. And that's what matters."