Excerpted from Managing Apple Devices: Deploying and Maintaining iOS 8 and OS X Yosemite Devices, Second Edition by Arek Dreyer and Kevin M. White
Mobile Device Management (MDM) is an umbrella term for any technologies that allow an administrator to manage devices remotely. MDM is also referred to as over-the-air (OTA) management because MDM functions are delivered over network connections that are commonly accessed via Wi-Fi or cellular connections. Although the abbreviations OTA and MDM are often used interchangeably, OTA more accurately refers to the act of deploying something remotely, whereas MDM describes the underlying technology that makes that deployment possible.
From an Apple perspective, MDM is the specific implementation used for remotely managing iOS and OS X devices. Using the developer documentation of MDM implementation, any vendor can create an MDM service to manage Apple devices.
Out of the box, Apple devices are not automatically managed by MDM solutions. The process of configuring an Apple device to use an MDM service is commonly referred to as enrollment. This process establishes a secure relationship between the device and the MDM service. After enrollment, most MDM functions are performed automatically, usually with no interruption of the user’s experience.