Heaving to  is a manoeuvre where you can leave the boat to its fate on the water without lowering the sails. Handy if there is an emergency situation on board, if you want some rest and your hands free. You can also reef the sail during heaving to. 
To make the boat heaving to we tack slowly but we leave the jib backed. The mainsheet is loose and we keep the boat on the new tack between close-reach  and  beam-reach. When the boat is stopped, we fix the tiller to leeward side The backed jib will prevent the boat from heading up to far so that the boat will not tack. The main sail and the helm position will prevent the boat bearing to far. When the  boat turns away from the wind, the boat will gain some speed and the rudder will make the boat heading up again until the backed jib pushes it away from the wind again. The boat will turn back and forth a little bit, moving forward real slow  but also drifts slowly to leeward. Make sure you have enough room on the leeside. If you heave to on a starboard tack, you have priority over cruising boats on port tack. Handy!