What does it mean when a monitor doesn't have a defined refresh rate?

[AesisVanex]

I'm currently using some cheap 1024x768 "monitor" (it's really a TV) at 60hz and so I'm looking into buying a proper monitor. I've been looking at the Iiyama Prolite E2483HS-B, mostly for its low price. It's got what I need, 1920x1080, HDMI inputs, its under 5ms but when I look at the refresh rate it says 55hz - 75hz. I can't seem to find much of an explanation for it online so I'm hoping someone here could explain to me why it's not a definite 60hz or 50hz. Ideally I'm looking for 60hz, I've just been thrown off by this a little bit.

Link to product http://www.scan.co.uk/products/24-iiyama-e2483hs-b1-black-led-gaming-monitor-hdmi-dvi-vga-1920x1080-50m1-250cd-m-2ms-speakers-vesa

 

[IInuyasha74]

Well that is weird. Unfortunately there is no real way to tell, but normally when there is a refresh rate range its able to do the lowest refresh rate, in this case 55Hz, at its highest resolution, in this case 1920x1080@55Hz. Then its likely that higher refresh rates are available as you lower resolution for example it likely will do 1680x1050@60Hz, and then 1440x900@75Hz.

It would probably be better to look and consider other displays.

 

[Suztera]

It is most likely a 60Hz at 1080p. Depends on your resolution, your refresh rate would be higher or lower.
Here are some timings: