Recently, I want to apply for a PhD position in a place which uses an online system to submit applications. The position is going be filled by either a PhD student or a Postdoc. There is a section in the application form titled "Research and teaching merits" with a mandatory field "Field of research". I wasn't sure what exactly I should write in this field so for now I left a '-' character there.
I searched on the internet but I couldn't find a clear answer about what I should write there. I also contacted the emails provided with the advertisement but there was no response.
What do you think I should write in this field of the application form?