Most household drainage works by gravity, which is why grade matters so much. Where a fixture or an area sits below the level of the drain it needs to reach, gravity alone will not do it and the water has to be pumped.
That applies to basements and below ground rooms, to some lower level bathrooms and laundries, and to surface water collecting in a pit that cannot drain away by itself.
The important difference from gravity drainage is that a pumped system has a failure mode. A gravity drain keeps working as long as it is clear. A pump stops when it loses power, when its float switch sticks, or when it fails mechanically, and the water it was moving then goes nowhere.
That makes maintenance meaningful rather than optional. Checking that a pump actually runs, that the float moves freely, and that the discharge line is clear, is the difference between a pump that works when needed and one that has been sitting idle and seized.
Where a failure would cause significant damage, a high water alarm gives warning before the water reaches anything.
If water is entering the house faster than it can drain, turn off the mains water, keep clear of any electrical fittings that are wet, and call for help. Do not try to clear a surcharging sewer or stormwater pit yourself, because the water can carry contamination and the pit may be deeper than it appears.
Water and electricity together are a serious hazard. If a leak is running near a switchboard, a power point, downlights or an electric hot water unit, switch off at the mains only if the switchboard itself is dry and safe to reach, then keep everyone clear and call a licensed plumber. An electrician may also be needed.