In Korean subjects are frequently marked by what is called a "subject marker." Sometimes the subject markers are left out but in most speech (especially formal speech), you will add a subject marker to a subject.

BIG NOTE - THERE ARE ALSO TOPIC AND OBJECT MARKERS (covered in a different lesson)

the subject markers are
이 & 가 (ee & ka)

The subject marker 이 is used when the subject that it is marking ends in a consonant sound.
EX -
이름이뭤입니까 ? - i-rum-i muosh-im-ni-kka? What is your name?

The subject in the above sentence is "name" and since "name" ends with a vowel sound AND it is the subject, it is followed by the marker 이.

The subject marker 가 is used when the subject that it is marking ends in a vowel sound.

EX -
나무가있읍니다 - na-mu-ga iss-um-ni-da - There is a tree.

wow this is kind of complicated....it'll take me some time to really get this, thanks though lance, i'm kinda slow..hhehe