In Thomson and plum-pudding model of the atom plums represent?

In the Thomson and plum-pudding model of the atom, "plums" represent electrons.

The plum-pudding model was proposed by the British physicist Joseph John Thomson in 1904. In this model, the atom was thought to be a uniform, positively charged sphere with electrons (the "plums") embedded in it. The electrons were thought to be distributed throughout the atom in a similar way to the way that plums are distributed in a plum pudding.