I think they are whatever you want them to be. Round here. half day trips predominantly on lanes or tracks, up to say 14km, mostly likely in shoes - I record as a walk. Cross country, probably greater than 14km, probably in boots I record as a hike. As far as I can tell, VR really doesn't care and if you are not publishing the outcome for use by 3rd parties, it doesn't matter. You could email VR and ask.