Above, someone mentioned rebar in the foundation. That is a Ufer Ground. In places with very dry soil you can pound a stack of ground rods into the earth and still not get a good ground. Ufer figured out that concrete in the foundation provides a good ground.

https://en.wikipedia.org/wiki/Ufer_ground

5 years ago I built my house and did my all my electrical, I needed a Ufer ground in the foundation and 2 ground rods near the meter. Being a newer area, water lines were plastic.

Generally in the US at least, on older houses it's just the water pipe, newer houses use a rod, very new houses use two rods because electrical code requires it now.

Rods definitely do corrode and need to be replaced regularly. ~10 years for zinc coated steel and ~40 years for copper coated steel rods.

Several different grounding electrodes can be used. It might be a literal rod buried in the ground, a group of 3 rods connected by copper wire, the cold water pipe, the steel structure connected to the concrete encased rebar in the foundation, if available, or a loop of wire buried in the ground surrounding the building.

They do get corroded and are supposed to be replaced every so often. Different materials are used depending on the type of soil to minimize the corrosion. If they're really fancy they might have a cathodic protection system to prevent corrosion.

When we were building our house, we installed an actual ground rod that the electrician connected--somewhere. I remember it being a literal rod getting pounded into the earth, pretty close to where we have the main power enter the house.

The water pipes are not metal at our house, so they would be of no use as an electrical ground.

This was in 2014, in Poland.