This is the downloadable library for the Pen package, which is a part of the Samsung Mobile SDK. Since this is just service APK, you cannot see its icon in the device even when it is installed. However, with the library installed, your application regarding SPen is able to use the latest Pen package features.
If the library is not installed on the device or the installed version is not the latest, your application using SPen displays a notification message. The message prompts the user to install or update the library, and opens the market to download the library.