You can store any data on it. Whether you can store the data from a particular app or not depends on the app - some allow you to change where they store data, some don't.
Since KitKat (that means Kit Kat and any later versions), the app that creates the folder on the card owns the folder (unless the phone is rooted - then you can change that). That means that you can't point an app to save data in an existing folder on the card.
But if you create the folder, you can copy anything you like to it - other than apps. Most apps won't run from the SD card, so to save themselves from having to answer a lot of "it doesn't work if I move it to the SD card" emails, they disable the capability.