From Bushwalk Australia
A pad is a track that is visible on the ground and has formed by the wear on the ground and vegetation of multiple people walking the same route. The track may or may not have any other markers such as Cairns, and may or may not be an officially recognised track.
Some tracks have markers but no visible pad (eg, if the track is not used enough for a pad to form or remain) and some tracks have a pad but no markers (eg, if the track is not an officially recognised track but has been used a lot due to common knowledge of the route).
A pad may also be referred to as a 'foot pad', particularly if it developed without any official track existing and without any track markers.
Note that foot pads without markers can be difficult to follow if the pad is not well worn, or becomes less well defined in some sections. In some cases it is very difficult to tell the difference between a foot pad made by humans and an animal track where animals use the same route repeatedly (forming an animal pad). Relying on foot pads as the sole source of navigation information can result in getting lost.
If following a vague pad that starts passing under vegetation far too low for you to walk upright, consider whether you may be following an animal pad.