Hill walking is the movement through and over hills and mountains without the planned use of a climbing rope or other climbing aids. It can take place within the UK or in any part of the world which has mountainous terrain. Outside the UK it is usually referred to as Trekking, but the principles are the same and the necessary skills similar.
Hill walking can take place under summer or winter conditions or, if outside the UK, even under desert or jungle conditions. Obviously the equipment, skills and experience required vary accordingly. Because walking is an everyday activity which we all do, the skills and experience needed are sometimes under-estimated and it is prudent to start from the assumption that it is quite different from a walk in the local park or along a canal tow-path. However mastering the skills needed is not difficult or overly technical.