It carries one normally-open and one normally-closed auxiliary contact (1 NO + 1 NC), fitting into a single 18 mm modular width unit on the DIN rail.
The 20 A rated operational current at AC is the continuous current the main contacts can carry under normal AC load — sized for resistive or moderate inductive loads like lighting banks, small heaters, or fan coils. The 230 V AC coil means the control voltage must be AC mains; don't feed it 24 V DC or it won't pull in. The 1 NO + 1 NC contact set gives you one auxiliary for status feedback and one for interlocks, which is typical for a simple on/off or auto/manual selector scheme. At 18 mm wide and 71 mm deep, this contactor occupies exactly one modular width on a DIN rail — the same footprint as a single-pole MCB. That matters when you're packing multiple devices into a crowded enclosure and every millimeter of rail space counts. The 90 mm height is standard for this form factor. The 1 000 W switching capacity for incandescent lamp load is a specific derating for tungsten-filament lamps, which have a high inrush current when cold. If you're switching lighting circuits, that's the number to size against, not the 20 A general rating.