Without finalizing, a DVD-R or DVD+R can not be played back by another playback device.
DVD Recorders generally have a menu that will lead you to the FINALIZE function.
Finalizing is typically found under MENU, SETTINGS, DISC, DISC EDIT, FUNCTIONS, OTHER FUNCTIONS or something similar.
DVD-R is the original home-recorded DVD format that is compatible with most playback devices. DVD+R is a later DVD format that is not always compatible with some older recording and/or playback devices. (The DVD+R format was first recognized by the DVD Forum as an official DVD format on 25 January 2008.) I use nothing but DVD-R DVDs for archival storage and duplication.