A mechanical switch current/voltage rating
When a mechanical switch is turned off the contacts separate, but the current tries to keep going (as an arc) until the gap is too large - then the current stops. The higher the current you're switching and the higher the circuit voltage, both will tend to keep the arc going for longer. So for a particular switch you can balance voltage and current ( as in your example ) - lower voltage lets you use higher current and vice versa.

If we assume the above is AC then you may also notice that the DC rated current for a particular switch is lower than the AC rated current - this is also due to how switching arcs develop. In AC the current drops through zero 100 or 120 times a second which helps the current to turn off, but DC doesn't have this 'help' and so the current rating for DC has to be lower.