The ring type joint flange is typically used in high pressure and/or high temperature services.
It has a groove on their face which can accommodate a ring type gasket.
As the bolts are tightened, they compress the ring type gasket and the gasket fills and seals the groove providing stronger joint connection.

Additional Information
Compared with FF and RF, RTJ, T&G and M&F provide stronger connection and better fit. However, they are more expensive than FF and RF, and commercial availabilty can be limited since FF and RF are most commonly used in the market.
In addition, when using T&G and/or M&F, the complexity of designing the piping system may increase since they have to be matched.
Same surface type should be used and it is not recommended to assemble with a different surface type (e.g., assembling RTJ with RF).
When not using the same surface type, a gap may exist in the gasket part and a trustable connection cannot be guaranteed, and thereby a leakage may occur.