Nylon has some desirable properties. It does not let ultraviolet light pass through it, and it is:
Unfortunately, nylon does not let water vapour pass through it either. This means nylon waterproof clothing traps sweat, so that after a while the inside of the clothing becomes wet, making it unpleasant to wear.
Gore-Tex® has the desirable properties of nylon, but is also 'breathable'. It lets water vapour from sweat pass to the outside, but it stops rain drops from passing to the inside. Clothing made of Gore-Tex® is very useful to hikers and other people who work or play outside.
Teflon® is the trade name for a polymer called polytetrafluoroethene, or PTFE. It is very slippery, so is used to make non-stick coatings for pans. It is also used in Gore-Tex®.
Gore-Tex® contains layers of nylon, PTFE and polyurethane. The PTFE contains a lot of tiny holes called pores - there are around 14 million per square millimetre. Each one is too small for water droplets to pass through, but big enough to let water molecules from sweat go through. Without the nylon, the layers would be too fragile to be useful.