[Spanish] Usage of yo

Hi all, I started learning Spanish from French but I switched to Spanish from English as a post described that the courses were much better with radio, stories… and that’s true, but it seems that the English course uses yo/tu/el in most cases when the French course made clear that they were to be used only when you want emphasis the subject. It’s very clear in French when you can add to your sentence. For example « moi, je mange » vs « je mange », in English they just say « I eat ». Can a Spanish speaking person tell me what is the actual usage of yo? Thanks!