Sata 3Rd plug

[chrissmith200579]

They are 3 plugs on the sata hdd what's the 3Rd one for please????

 

[scout_03]

this on is round molex connector https://www.ferniefix.com/article/community/hdd-vs-ssd-vs-shdd and this one is regular sata one https://www.pcbuildadvisor.com/how-to-install-sata-hard-drive/