It's useful to look at this first, to give us something to compare to ferns. The male pollen cell carries half the genetic material of the adult plant and fuses its genetic material with that of the female cell, which carries the other half. The complete, fertilised cell grows into the seed, which, when ripe and when it finds itself in suitable soil and moisture, is capable of producing a complete adult plant. The seeds themselves are often very durable, able to wait for long periods in adverse conditions before they grow. So the higher vascular plants have evolved to occupy nearly every niche on the land surface of the earth.
Ferns do it differently.
They have a more complicated method that depends on there being liquid water for the process to complete. To detail this, I'll need to describe some of the parts of a fern. The leafy branch of the fern is usually called a frond. The small leaflets that make up the whole frond are called pinnae. If you look underneath a fern frond, you will often see small clumps, spots or patches that look like they are stuck onto the under surface of the pinnae.