The PWR fan header is likely used to monitor the activity of the power supply fan.
The extra case fans can be plugged directly to the power supply, given there are enough leads elsewise a splitter is used.
How many fans will one MB fan header accept?
There are 3 headers (mb connectors): pwrfan, chfan and cpufan.
The case I want has 4 fans, two up front and two in back. How can I connect them all when there are only 3 headers? Is it like hooking up components to a power supply with splitters? And what is the "pwrfan".