While searching for fuse holders in the web, I found an infinity of pages like this, where the rating of the fuse holder is e.g.: "10A/250V AC, 15A/125V AC" (it is an example, values do not matter). I can't figure out what is the meaning these ratings: For the current rating, I can understand that the fuse holder can support at most e.g. 10A, since the contact between the fuse and the fuse holder has a small resistance that generates heat when crossed by big currents. But in this case, this rating should depend only on the current and not on the potential, so why a potential of 125V in the example above allows the larger current 15A? Moreover, the spec "AC" for the fuse holder is rather strange: what has a fuse holder to do with AC or DC ?
Fuses first: -
Fuses do need/have a voltage rating - you wouldn't use a fuse that is only qualified for 125V on a 230V AC system. A fuse that is specified for only 125V AC may fail to "break" adequately at 250V AC. These are safety devices after all.
You'll probably also find that some fuses have a "high-rupture-current" rating too. This defines the sudden massive surge of current that may cause a lesser fuse to form a plasma inside the glass/ceramic tube and therefore still conduct and be unsafe.
They have to handle the current and they have to not go unsafe on the voltage that may be placed across them.
Since a fuseholder's contacts are resistive, and ohmic, increasing the voltage across them will cause the current through them to increase as well.
That increase in current will increase the \$ I^2 R\$ losses, causing the contacts to heat up and, since the contacts are in intimate electrical and thermal contact with the fuse's metallic contacts, much of that heat will be conducted into the fuse element itself, which will cause its temperature to rise, but not solely due to just the current through the fusible element.