What's the meaning of ' El mundo sería mejor, si hubieran más gente como tú. '?

Espero que te mejores ahora. Esta semana descansas en casa.     

Question about verbs. I've got a verb book but unfortunately it's entirely in Español, and does not give examples of conjugated verbs in use. I read the subjunctive thread but am still confused! I also don't know what "potencial simple" means. Can you give me an example of the potencial simple, presente de subjunctivo and imperfecto de subjunctivo (plus their compound tenses) in the verb HABLAR, please? Also, why does the imperfecto de subjunctivo have two sets of tenses? Muchas gracias

现在流行的“网闹”是什么？