I am guessing RGB lighting. But, providing us with Phanteks model and a motherboard model would help.
The mobo is asus prime x470-pro. The block is aIndustry standard RGB-4PIN Adapter Included for synchronization with RGB motherboards.
There are 14 different Phanteks GPU blocks and hundreds of different motherboards.
But they’re both male connectors. Do I need to buy an adapter?The manual for that waterblock says "RGB LED Cable -- QTY: 1" Confirmed RGB cable.
Page 1-2 of your motherboard manual shows two RGB connectors. One next to the AIO pump connector and one on the edge of the board near CHA_FAN2