Beta tester is the person who can try new features and apps before they are publically released for other users.
Why whatsapp is providing beta testing service?
Whatsapp and many other companies want to get review about the feature or app they are going to release before it was publically introduced to all the users.
How to become a beta tester for whatsapp?
3)Click on the app page.
4)Scroll down to the developer option.
5)Click on “become a beta tester”.
6)You can now get the latest updates about the app version.
7)You can also be able to leave the beta program and become a normal user.