MTP stands for "Media Transfer Protocol." MTP was developed as a standard protocol that allows media devices to transfer information to programs such as Windows Media Player. It allows the computer to see only the audio and media files instead of the entire file system.
MTP works in a different way than USB mass storage devices. USB devices share their entire file directory, exposing even system files and important programs to the computer. MTP exposes only selected files to the computer, meaning that there is no way to alter the system files when in media programs like iTunes. This prohibits the deletion of key files.