BYOD
Bring Your Own Device
A program / policy that allows you to use your own, existing personal device (such as a phone) instead of receiving a new device issued by a company or organization.
When signing up for cellular service from a new company (carrier), this would mean activating the new service on an unlocked phone that you already own. That device may have been purchased unlocked from a third party, or previously used with a different carrier (and now unlocked).
In the context of using a device for work, BYOD is an alternative to carrying a separate, company-issued "work phone" (for example). Instead, it lets you use a personal phone for work tasks in a way that keeps employer data secure and personal data private. This is accomplished by essentially partitioning the phone into two phones in software, at the OS level; the result is effectively a virtual "work phone" inside your personal phone.
This is a feature of the OS that works in tandem with MDM (Mobile Device Management), a centralized system that lets organizations remotely manage employees' mobile devices.
See: MDM
