Apps are installed to this storage, labeled as Internal storage in your phone settings. It also stores data such as your text messages, contacts you created or synchronized to your phone, account settings, and more. This storage is managed and carefully guarded by your phone since it contains your private information. When you connect your phone to your computer, this storage is not accessible from your computer. Storage contents will be erased when you do a factory reset. Make sure to back up your data before starting a factory reset. Some apps allow you to back up to your storage card, such as People.
This is another built-in storage, labeled as Phone storage in your phone settings. This is where you can store your files. When you connect your phone to your computer, this storage is accessible and you can copy files between them. When you do a factory reset, you can choose whether to keep or erase the storage contents.