Todo el mundo va en bus.=Se va en bus.
La gente habla inglés.=Se habla inglés.
Las personas viven en las ciudades.=Se vive en las ciudades.
Nadie come verduras.=No se comen verduras.
La gente lee menos.=Se lee menos.
Sometimes we don't want to specify who is doing the action, as in the right column of the examples above.
And why don't we want to specify who is doing the action?
To generalize what we're saying. We have words like la gente or todo el mundo that can also be used for that. But, to be honest, using se sounds more natural.
And can I generalize with se just by placing it before the verb?
Sí. You just have to keep an eye on what you're talking about, like in the "verduras" example: "comen" is also plural.
I think I get it. So what's most important is the thing you eat, you speak or you read.
Yes, look at those examples:
Se dice que hay que hacer mucho deporte.
It is said that you have to do a lot of sport.
Se comen muchas grasas y poca fruta.
A lot of fats and little fruit are eaten.
Se buscan muchos camareros en los restaurantes.
Many waiters are sought after in restaurants.
Se vende el coche usado del vecino.
The neighbor's car is being sold.
Se is a special word. In Spanish it has several meanings, that's why we will see them step by step along our curriculum.