B4A is an IDE to build app for Android, before it was called Basic4Android. The code is made in text mode with a syntax similar to that of Visual BASIC 6.0. Until now it was priced at about $ 50, but now it is 100% free (gratis).
B4i, is to make app for iOS.
In these pages I have put examples so you can see how to do it.
I tried B4A but could not use the developer IDE on my MAC, because it runs only on Windows. You should also know that you need a MAC to build the load modules for iOS yourself. Otherwise you can have the load module built by the B4A for you.