ISOMETRIC DRAWINGS
Views use 30 degrees for lines showing      'horizontals' of the object:

This is the most widely used drawing convention and you should be very confident that you know what the term 'Isometric' means. 
It can sometimes be seen described as a 'pictorial' view.  Examination questions asking for a 'pictorial view' mean an 'isometric'

PLANOMETRIC DRAWINGS

This convention can be exceptionally useful as the drawing is 'built-up' from an actual plan.  If a ground floor map of a room is completed and all the walls are shown as flat panels - vertical to the first 'view' - then a PLANOMETRIC view has been started.  One big advantage of this drawing style is that all circles still appear as circles on the finished sketch, whereas on an isometric they will appear squashed.  If measurements need to be taken straight from the drawing, it is obviously easier as you can simply
measure everything on the paper and then use the scale.