<em>"Annyeonghaseyo ___ imnida" and "Annyeonghaseyo jeoneun ___ imnida" both have different definitions.</em>
"Annyeonghaseyo? Jeoneun <em>Bob* - </em>imnida" is the formal way of introducing yourself in Korean (to your parents, teachers, etc).
When you introduce yourself casually, you take out "jeoneun".
"Annyeonghaseyo? <em>Bob - </em>imnida."
<em>*Bob (name) is used as an example. </em>
