Line out on back of pc

[Superlp12]

Pretty confused on headphone connection. On my previous z270(gigabyte gaming 7) motherboard, it has a separate output marked headphone for which Plug in my headphone. If i plug it into the front line out, there will be no sound. On my current z370(gigabyte z370 gaming7), there is no separate headphone out. The manual says plug either a headphone or speaker into the front line out and it did work well for Hd800 headphone. why is that so? My understanding is that line out means not powered.

 

[Phillip Corcoran]

http://www.tomshardware.co.uk/answers/id-2712430/line-headphone.html

 

[jsmithepa]

PC line outs often have *just* enough power to drive headphones. No guarantee.