The Apple Developer Program is a paid membership from Apple, not a piece of software. An individual or an organization enrolls, and the membership gives the right to distribute apps and games on the App Store for iPhone, iPad, Mac, Apple TV, Apple Vision Pro and Apple Watch, plus access to Apple's developer services. A free Apple developer account, without the membership, only allows beta software, testing on one's own devices and the forums.
Members get beta versions of Apple's operating systems and Xcode, app services such as In-App Purchase and Apple Pay, TestFlight for up to 10,000 external beta testers, App Analytics and sales reports in App Store Connect, and code-level technical support. Through the App Store, an app reaches users in 175 regions, and Apple handles worldwide payment processing and hosting. Mac apps can also be distributed outside the Mac App Store with a Developer ID certificate and Apple's notarization.
It is an annual membership fee. Organizations that distribute apps only to their own employees can use the separate Apple Developer Enterprise Program.