My trainees generally see me teaching everyday lessons. Sometimes, if the situation arises, they see me teaching a demo/observed lesson. There isn't a vast difference other than I write a fuller plan and make sure everything is perfect in the demo lesson. For my trainees I see their everyday teaching all week, but once a week I 'observe' them and so want to see them pulling out all the stops. I want them to care that they are being observed and so do the very best they possibly can, probably at a standard they couldn't sustain all week.