When you click in button "OK" the description grid view is closed and all changes are automatically saved in the database. If you did some changes and want to save them without leaving the form, simply click on (see image below). If you close the window, e.g. by clicking the "Cancel" button, and still have unsaved changes, you will be asked to save or discard the changes.
You may discard all unsaved changes without leaving the form by clicking the button and the data will be reloaded form the database (see image below).