There are various classification systems out there, depending on where you are. British classes are

Class A: Solids

Class B: Liquids

Class D: Metals

Class E: Electrical equipment

Class F: Cooking Fats & Oils

In the US system, the fifth is Class K, which is Cooking oils and fats. Same classes, different letters and swapped order between metals and electrical.

And not that electrical as a source is not what makes a class C (UK class E) fire. Electrical sparks can start any type/class. To be classed as a class C means the fire is inside some electrical system or components, where you don’t want to use any kind of conductive material like water or foam to put it out