Example of instance variable:
class of "horse" has an instance variable called "hair_color"
you can have a few instance of horses,
horse number one "hair_color" = WHITE
horse number two "hair color" = BLACK
Example of static variable:
class of "horse" has a static variable called "no_of_legs"
once you set "no_of_legs" = 4
all horses have got 4 legs.