To whom it may concern,

I am a Filipino currently working here in Changzhou, Jiangsu province for almost 2 years. I am planning to visit Seoul Korea during the summer vacation to see some of my students. I already read some of the information on the internet on regarding C-3 visa to visit Korea. However, I would just like to know what kind of document means 'verifying the purpose of his/her visit to Korea'? Does it mean I have to get an invitation from my student? Or does it mean that I need to just write a letter to the Korean embassy asking if I can visit Korea?

Thanks a lot for your time.