First of all, you must know that the verb gustar is a special verb, because the subject is the thing that you like and not the person that likes something: I like sugar: el azúcar me gusta/me gusta el azúcar. I like cars: los coches me gustan/me gustan los coches So gustA/gustAN is the third person singular and plural, respectively. That means that for the verb gustar, the most important conjugations are the third person singular and plural, representing the thing-s that someone likes. In the past, the third person singular is "gustó", and plural "gustaron". To know WHO likes something, we use the indirect object (me, te, le, nos, os, les). So, we say, in the past: me/te/le/nos/os/les gustó/gustaron. So, even if you can conjugate the verb gustar in all persons (yo gusté (a alquien), tú gustaste, el gustó, nosotros gustamos, vosotros gustásteis, ellos gustaron), there no sense in concentrating to study it, because these forms are not commonly used, in the same way that you don't say: I am liked yif you want to say "Someone likes me". Hope it helps.:)

Pretérito imperfecto (action is yet in progress) yo gustaba tú gustabas él; ella; usted gustaba nosotros; nosotras gustábamos vosotros; vosotras gustabais ellos; ellas; ustedes gustaban Pretérito indefinido (action is finished) yo gusté tú gustaste él; ella; usted gustó nosotros; nosotras gustamos vosotros; vosotras gustasteis ellos; ellas; ustedes gustaron http://www.esfacil.eu/es/verbos/conjugacion/144-gustar.html

http://conjugador.reverso.net/conjugacion-espanol-verbo-gustar.html