GB is a modified version of the popular messaging app WA. It offers a number of additional features that are not available in the official, such as:

Dual accounts: You can run two separate instances of GB on the same device, allowing you to have two different accounts signed in at the same time.
Increased file size limits: You can send and receive files up to 100MB in size, compared to the 16MB limit in the official app.
Custom themes: You can choose from a variety of made themes, or create your own custom theme.
Other features: GB also includes a number of other features, such as the ability to hide your online status, change the font size, and more.
GB is not an official app from WA, and it is not available on the Google Play Store. However, it can be downloaded from a number of third-party sites.

Here is a more detailed description of the features of GB:

Dual accounts: This feature allows you to run two separate instances of GB on the same device, allowing you to have two different accounts signed in at the same time. This can be useful if you want to keep your personal and business accounts separate, or if you want to use two different numbers on the same device.
Increased file size limits: The official WA app limits the size of files that can be sent and received to 16MB. GB increases this limit to 100MB, allowing you to send and receive larger files, such as videos and photos.
Custom themes: GB includes a number of made themes that you can choose from, or you can create your own custom theme. This allows you to change the look and feel of GB to match your personal style.
Other features: In addition to the features mentioned above, GB also includes a number of other features, such as the ability to hide your online status, change the font size, and more.