Shape as basic element of art/design, a flat area surrounded by edges or an outline that can be of any type, organic or bio-morphic.
Organic(bio-morphic)- As natural These are natural things like leaves, cloud etc, those which have irregular shapes unlike geometrical are bio-morphic shapes or organic shapes.I read somewhere what is meaning of bio-morphic and it is bio(life) + morph (form). So basically natural things which are not manipulated on regular shapes or height width are called organic shapes.
Geometric Shapes- like rectangle, triangle, square etc.. mostly used by human on arts because the are easy to draw and easy to create pattern. so you might seen them on your walls of your house as as formation of design. Every geometric shape has its own set of properties like its length, height, angle. So if you are trying to draw a triangle, it must have 3 sides, for square and rectangle 4 sides etc.
Positive/Negative shapes & Implied Shapes – When talking about positive and negative what comes first in mind? that they are opposites, right? Yes it is the fact that when you create an shape, the actual shape is called positive shape but if you look closely the left space itself creates a shape is called negative shape. Its like a window frame, window frame itself is a shape, but the inner space of frame itself is creating another shape and it is negative shape.
From here the concept of implied shapes were created, that when you create shapes in a regular basis that the negative space itself give us the feel of an individual shape, it is called implied shapes. In this image if you see there are number of rectangle created in a way that the middle space gives feel of a circle, isn’t it?
So it is just simple as that, go start playing with shapes like you used to in your childhood, try to create pattern from shapes and grab deep understanding of shapes. Enjoy.