It's the part that sits between the contactor and the motor, watching current and protecting the winding from sustained overcurrent.
The auxiliary contact ratings tell you what the signal side can handle: 2 A at 24 V, 2 A at 230 V, and 1 A at 400 V. The power dissipation per pole is 2.2 W, so three poles running at full load dump about 6.6 W into the enclosure — factor that into your panel thermal budget. The overload relay mounts directly onto the contactor, which saves DIN-rail space and keeps the power wiring short. Size S00 is the smallest SIRIUS frame, so it pairs with the S00 contactor range. The screw terminals accept 2×(0.5…1.5 mm²) or 2×(0.75…2.5 mm²) solid or stranded wire, and the screwdriver spec is Pozidriv PZ2 with a 5–6 mm shaft diameter.
Temperature compensation is active from -40 to +60 °C, so the trip curve stays accurate across the working range. The substance prohibition date of 10/01/2009 indicates RoHS compliance — the part was designed to meet the 2009 deadline for restricted substances.