During the middle ages reconnaissance played at least a minor part in a tactician's plans. As evidenced by this question Irish Hobelars would be used to scout ahead in terrain that was too difficult for heavy cavalry to traverse. But apart from this type of light cavalry I have not heard of any implementation of scout troops beyond seeing that occasional reports were returned by scouting forces.
How was reconnaissance performed during medieval marches? Did scouts ride ahead far enough to set camp and wait for their army to catch up to them, or would they perform scouting missions and return to the main force in one full outing? Similarly, what were their main tasks? Identify the opposing force, identify advantageous terrain, or perform other operations?
For the purposes of the question I'm curious about how scouting was performed during the period of the Hundred Year's war as I am interested to determine if that predates modern scouting techniques or if the it has remained relatively consistent over time.