Meaning of 'per indicare il cavallo'

could anyone explain what this phrase means? cavallo normally horse but in this context i’m confused?

Per indicare il cavallo, il latino scritto usava la parola equus, mentre il latino parlato usava la parola caballus. L’italiano, come vedete, continua la forma del latino parlato.

The meaning of the sentence is that the latin word for horse is equus.
“Indicare” in this case is used figuratively. So it literally means that to signify a horse, written latin used the word “equus”.

It’s quite a common way to use “indicare”, great word to know!