Germanium (Ge) is a chemical element with atomic number 32. There are several germanium isotopes, but 74Ge (32 protons, 42 neutrons) is the most abundant.
Just like silicon, which is in the same group in the periodic table, germanium is a semiconductor which can be used in transistors. Germanium was used a lot early in early transitors, but was later replaced by silicon since silicon has better electrical properties and is also significantly more abundant and therefore cheaper.
Modern day application of germanium include fibre optics and LED lights.
The name germanium comes from the element's discoverer, Clemens Winkler, who was a German chemist.