What plant is non-flowering plant?

The most popular non-flowering plants are probably mosses, ferns, and conifers (example: pine trees).

and what they are are plants that have no flowers

Yes, that is exactly right. Plants with no flowers. Plants without flowers will reproduce by a naked seed (gymnosperms, like conifers), which is a seed without a flower (flowering plants have their seed encased in the ovary of the flower during pollination), or by spores (ferns, mosses).