Heterosporous means the production of two types of spores.
Spores are generally small microspores and large macrospores(megaspores).
Heterosporous plants produce spores of two different sizes which are the large spores called the megaspores, which function as female spores, and the small spores known as the microspores which function as male spores.
Heterosporous plants usually give rise to the two kinds of spores from within separate sporangia, one is a megasporangium that produces megaspores and another one is a microsporangium that produces microspores.
When sporophytes produce spores of two different sexes and sizes, it is called heterospory.