Bitrix Framework - is a core PHP-based platform for the development, creation and management of various web projects. Such platform allows creating an unlimited number of projects using a single copy (license) of the product, by allocating a single copy of the core and the system database on a server.
Presently, not all capabilities of the old core have been duplicated in D7. However, the new core D7 in Bitrix24 Framework gradually replaces the "old" core. When using the "old" core has triggered such IDE warning: Method/class is deprecated, it means that D7 methods must be used.
Due to multiple reasons, API documentation may not encompass all methods. To improve one's understanding, its sometimes better to carefully review the software code directly.
Please, be advised, this documentation is provided for educational and referential purposes only. Detail descriptions of the system's operational principles are provided in Bitrix Framework learning course.