http://www.tpub.com/content/engineering/14069/img/14069_187_1.jpg (oblique 3rd one)
http://www.bbc.co.uk/schools/gcsebitesize/design/images/dt_g_dmi_tp6.gif (isometric 1st top right side one)
http:/www.internationalkitchen.com/kitchens/perspective.GIF (perpective 4th one)
http://www.tpub.com/steelworker1/14250_files/image054.jpg ( orthographic 2nd one top left side one)
Isometric is a pictorial view of a 3 dimensional object. There are 3 coordinate axes that are viewed in a way that the angles of projection are 120 degrees.
Perspective is a geometric method of representing objects that are actually 3 dimensional in 2 dimensional. For example making objects appear smaller the further they are.
Oblique is a type of graphical projection. It produces an image by intersecting parallel rays using 2 dimensional images of 3 dimensional images.
Orthographic is a view from only one side of an image.( front, back or side) Thus, it takes several views to view the entire object.