Most seminaries these days have a requirement that seminarians wear clerical dress in the Theologate (graduate theology studies). From what I understand, it comes from a long tradition of seminarians wearing clerical dress prior to ordination, a practice that fell out of favor for a while. Pope John Paul II (1982) mandated that every seminarian in Rome who had received candidacy to wear clerical dress, regardless of his home diocese. The practice gradually spread to the rest of the world re-adopting the practice.
These days, the application is fairly wide. At some seminaries, candidacy is a third-year rite, just before diaconate. At others, candidacy is a first-year requirement of theology. Some wear clerical dress throughout theology, or only part. Some wear clerical dress only at ordination to the diaconate. Some seminaries require clerical dress all the time on seminary grounds; others only at formal functions or class, or various functions. Typically in the US, clerical dress is not worn by seminarians outside of the seminary except specific instances, but that is an old US practice somewhat unique to us here. I don't know about the rest of the world. Wearing clerics helps the seminarian adopt the identity of spiritual father, and helps remind him that he is never "off-duty," and cannot remove the identity of the priest like a uniform. There's a lot of discussion on this in various places, but I hope this answers your question.
Congratulations on your discernment. May God fill you with his love, and give you peace in knowing his will.