What is the difference between "walking" and "hiking?" For me, I just prefer to say I'm hiking because "speed walking" to me conjures up an image of a middle-aged man in Speedos, swinging his hips and pumping his arms up and down...not an image I want to have! But actually, I believe the only difference is whether or not you are on a trail. If you are on a man-made track or a road, you are walking; if you are on a dirt trail surrounded by nature...I'd say you are "hiking."
All that being said, walking/hiking is nothing to be ashamed of. For some reason many people look down on walking, but a brisk walk can produce most of the same health benefits as running and produce a lot less injuries. Besides that, even many runners who take brief walk breaks have proven to drastically improve their longer distance "runs" because they don't tire so fast and slow down at the end of their run, but they have a more steady, consistent pace throughout the race. Also, I found early on in my attempt to become a runner that I simply enjoyed the experience better when I slowed down.
So don't be afraid to walk. In fact, you might want to get your walk down before you start adding brief jogs. Shoot for a continuous 15 minute-per-mile pace Eventually, you may decide to run, but even then you may look forward to some brief walk breaks. Until that point, just get out there and get moving!