Have you ever seen a silver-colored fence or gate outside that has a slightly rough texture? That might have been hot-dip galvanized.
Hot-dip galvanizing is a way of coating steel (a metal) with another metal called zinc. Zinc helps to protect the steel from rust and other things that might harm it. By dipping the steel into a hot bath of liquid zinc, the zinc sticks to the steel and makes a barrier between the steel and anything that might harm it.
It's like putting a jacket on when you go outside on a cold day. Your jacket keeps you warm and protected from the cold air, and hot-dip galvanizing helps to keep steel protected from things like water, oxygen, and other things that might harm it.
Hot-dip galvanizing works really well, so many things are made out of galvanized steel. Railings, fences, streetlights, signs, and even things like car parts can be hot-dip galvanized to protect them from rust so that they last longer.