Answer:
The conjugation of the verb. "falta" or "disgusta" means to one person (singular conjugation of the verb), but when you add an "n" to these verbs, these ones become plural
Some examples could be:
"Ella come pizza" (she eats pizza)
"Ellos comen pizza" (they eat pizza)
The difference is about the people you are referring to (either one or more than one)
Hope I could help :)