On an Android device, SO files are stored within the APK under /lib//. Here, "ABI" can be a folder called armeabi, armeabi-v7a, arm64-v8a, mips, mips64, x86, or x86_64. The SO files within the correct folder that pertains to the device, are what's used when the apps are installed via the APK file.
Shared Library files are sometimes called dynamically linked shared object libraries, shared objects, shared libraries and shared object libraries.
