Quote Originally Posted by Antonio1986 View Post
So the one can stand alone the other cannot.
съесть + type of food
поесть + nothing
You can say "Я поел бутербродов" but unlikely "Я поел бутерброд" (though it becomes more likely if бутерброд is VERY big). Бутерброды here treated as uncountable.

I'd say that "поесть" means "to spend some time eating".