BusyBox is a package that contains various UNIX utilities which might be required by certain applications to run on your Android mobile device. You can see a list of the included tools by accesing the straightforward user interface. Here, you are allowed to install and uninstall various packages. In case you have a rooted smartphone and you plan to use certain applications, you should consider adding BusyBox to your device's memory.
It's also possible to go for a Pro version that provides additional features, like Advance Smart install, backup function, being able to choose which applets you want to be added, uninstall feature, and more.