Spores are the seed-like cells that help some kinds of plants and bacteria to reproduce. Ferns and mosses reproduce using spores.
Many plants reproduce by means of flowers, which make seeds. Most plants that don't produce seeds use spores to spread themselves around. Spores are microscopic, and plants like mosses and ferns make huge quantities of spores, which are blown around by the wind so they can grow in new places. Spore comes from the Greek spora, "seed-time" or "a sowing."