Here's some 'splaining:
From the All Gender Health Online website:
By participating in this study, you help us understand and increase awareness of the sexual health of non-transgender men who have sex with transgender people. Findings from this study will be used to develop an online intervention to prevent HIV infection and transmission among transgender people and their partners, such as yourself.
If you're interested or have any questions, visit the site here: https://www.allgenderhealth.org/TGHome.aspx