>4K
Great in combination with a PC, useless for consoles/blu-ray players/streaming shit
>120hz/240hz/9000hz
It's 60hz + upscaling. Not necessarily a bad thing, it makes the picture look smoother while the GPU only needs to render at 60fps. Not always accurate though.
>contrast ratio
Higher contrast means better/purer colors.
Also deeper black levels, useful for movies as they contain a lot of dark scenes. OLED is perfect, VA is great, IPS is acceptable.