This is Tags, a feature that is not common in instant messenger applications, but which WhatsApp wants to implement so that users can better organize both chats and messages.
As the site is mentioned, we can create up to 20 labels of different colors for chats and messages, and we can edit them and put the name with which we want to identify the label.
For example, if in the chat of your friends where you have a repertoire of memes, and you want to identify only the memes that deal with the World Cup, then you create a label in that message, you put the name and that's it, and you can do the same with futures messages.
To create a label we must press a message or chat, press the option Labels and add the name to the label.
In the case that we want to look for a label, we simply have to go to the magnifying glass, located in the chat section in the upper right, place the sign of#and then the name of the label.
We can also edit the labels, delete messages from the labels or change their name, all from the menu option.
It is important to mention that the label tool is not yet available, but it seems that it is about to arrive in a very short time because the fact that the company has placed this function in its FAQ, speaks of its imminent launch.