Main Vocalist: The vocalist with the best technique. They often get the most lines, get the hardest singing parts, and sing the chorus. Sometimes, the main vocalist will ad-lib on the chorus. (EX: EXO's Chen, Red Velvet's Wendy)
Lead Vocalist, #2: The Vocalist that has the 2nd best technique, after the main vocalist. They get a good amount of lines, and may sing the chorus while the main vocalist does ad-libs.
Vocalist: Vocalists often support main/lead vocalists with backup singing, but may also get a fair amount of lines depending on the group.
Sub-Vocalist: Sub-Vocalists support the main/lead vocalists with backup singing lines, and get fewer lines.
Lead Rapper: The rapper with the second best technique. Sometimes on rap parts, the lead rapper will start before the main rapper.
Rapper, #3: A rapper sometimes considered to be a rapper, but not as good as the lead and main. May not rap alot.
Sub-Rapper, #4: Sub-Rappers are supposed to be better rappers than the non-rapping members, but not enough to have a higher rank.
Lead Dancer, #2: The dancer with the 2nd best dancing skills. When the group dances together, the lead dancers may be found in the front.
Dancer, Placeholder: Technically, there is no “dancer” or “sub-dancer” position. They are just placeholders for the main/lead position.
Visual: Pretty much the eye-candy. They are considered the most attractive based on Korean beauty standards.
Center: They are usually in the front/center during promotions or video shoots. Be it because of their good looks, popularity, or dancing skill. The center can change with each comeback. A specific member is always in the center at one point.
Face of the Group: They are often mistaken for visuals, as their job is to bring attention and popularity to the group. They will often be invited to represent their group in variety shows, or represent the group at public events.
Leader: The one that motivates, cares for, and represents their group on stage or at award festivities. They are supposed to be mature and charismatic to gain the members’ trust. They might be one of the eldest members, or the one who trained the longest.
Maknae: The Korean word for someone who is the relative “youngest”. Nothing too special to it. Just literally the youngest member or of the group. Some groups have more than one maknae if they are born in the same year but most don't.