Before the discovery of electrons how were charges thought of?

Before the discovery of electrons, electric charges were thought to be some sort of magnetic effect.

Ancient cultures knew that rubbing cat’s fur on amber rods could attract light objects like feathers. Around 600 BC, Thales of Miletus guessed that friction made amber magnetic.

In 1600, the English scientist William Gilbert studied electricity and magnetism. He coined the word electricus ("like amber", from electron, the Greek word for amber) to refer to the property of attracting small objects after being rubbed.

In 1838, Michael Faraday found that forcing electricity through a partially evacuated glass tube made the gas glow. He called the glow cathode rays.

In 1891, G. J. Stoney did many experiments involving electricity. He proposed the term electron to describe the fundamental unit of electrical charge.

J. J. Thomson built many cathode ray tubes and built on Stoney’s experiments. In 1897, he showed that the flow of electricity in cathode ray tubes consisted of streams of electrons.

Once electricity was understood as a flow of electrons, scientists, engineers, and inventors were able to turn it from a scientific curiosity into an essential tool for modern life.