The Siemens 5SU1156-1KV06 is a combined residual-current device and miniature circuit breaker (RCD/MCB) — what Siemens calls an FI/LS protector.
The 10 mA sensitivity is the most sensitive common threshold; it's specified for circuits where even a small leakage to ground must be caught quickly, such as wet-location outlets or medical-grade sockets.
This is a 1+N-pole unit — it switches and protects the line conductor while the neutral is switched but not protected. The 70 mm depth (D=70MM) fits standard DIN-rail enclosures; it occupies a single modular width on the rail. In a distribution board, it's typically the final sub-circuit device, combining earth-leakage and overcurrent protection in one module to save rail space.