A signboard is a flat board with writing or pictures on it that gives you information or shows you where to go.
Signboards are helpful because they give us important information.
Examples:
The signboard says the library is that way.
We looked at the signboard to find the way to the zoo.
The signboard near the road tells us how far the next town is.
The signboard at the store shows us what they sell.
The big signboard at the park tells us about the animals.
The signboard on the bus tells us where it's going.