Question

what are plants that have their seeds enclosed in an ovary??

Answer 1

Ovaries are fruits or plants, and the type of plant that has the seeds enclosed in ovaries is called an angiosperm.
The contrast of angiosperms are gymnosperms, who's seeds develop in pinecones, in an unenclosed condition.

Answer 2

See it like the difference between an apple and a pinecone. The seeds in the apple (angiosperm) are inside the fruit, and you can't see them from the outside. While the seeds of the gymnosperm are in the pinecone, you can see them from the outside because they're not enclosed in the ovary.