The STMicroelectronics STPR1520D is a fast-recovery epitaxial rectifier diode rated for 15 A average forward current and 200 V repetitive reverse voltage. Its 30 ns reverse recovery time puts it in the class of ultrafast rectifiers suitable for switching power supplies operating above 50 kHz — think PFC boost stages, flyback secondary-side rectification, and output OR-ing diodes in 100–150 W off-line converters. It is a single-junction standard diode, not a dual or center-tap pair.
The 30 ns reverse recovery time (trr) is the spec that separates this from a standard 50/60 Hz rectifier. In a 100 kHz hard-switched converter, a trr of 30 ns keeps the reverse-recovery charge low enough that the MOSFET or IGBT doesn't see excessive turn-on loss or ringing. The 15 A average rating is continuous — the device can handle repetitive surge currents higher than that, but the TO-220AC case needs a heatsink for any sustained load above a few amps. Forward voltage drop is 1.25 V maximum at 30 A pulsed (not continuous), so expect around 0.9–1.0 V at 15 A continuous; that's about 15 W of dissipation, which a modest clip-on heatsink can manage. Reverse leakage is 50 µA at 200 V, which is fine for offline applications.
If you are designing a new board, look at ST's current fast-recovery rectifier family in TO-220AC (e.g. STTH series) for a pin-compatible alternative with similar or better trr, but verify the forward voltage and current rating against your thermal budget.