both start with pizza dough.
a calzone is pizza dough rolled out into a circle, and the fillings are placed on half of it. it's folded over and the edges crimped, forming a half moon shape. then it's either fried or baked.
a stromboli is pizza dough rolled out into a long rectangle(ish) shape, fillings placed along it's length, then it's rolled and the seam crimped, so that the fillings are enclosed. if you sliced it, it would resemble a cinnamon roll, except with the different fillings. usually they're baked, but i guess you could fry smaller ones.
A true lover of nature does not despair now that his mistress has turned a colder cheek.