Whatsapp has recently launched its beta version for multiple device support. Now you make connections with the same mobile number on 4 different devices. In simple words, you can use your favorite WhatsApp web without online your primary device. 
Do you want to use this feature? It is very simple to join first update your WhatsApp application. Then go to linked devices. There must have a beta user option. There you can join. If you don't have such type of option. You have to wait for the first rollout of this feature.
I hope you will get a basic idea of how you can join the WhatsApp beta community and also how you can get multiple device support in WhatsApp like telegram and signal.