A sign is a non-solid block that can display text. A sign can also be used to block or redirect the flow of water or lava while still allowing entities to pass.
To craft a sign, the player should place six wooden planks in the top six slots of a crafting table and one stick in the bottom middle slot. This crafting process will create 3 signs at a time.
The main objective of signs and banners in Minecraft is for the players to leave messages for each other or the rules for an adventure map. It is also possible to use banners and signs as ornamental items used to decorate your home or warn players about dangerous areas.
For the complete guide on signs, click the below article.
How to make Signs in Minecraft