Rec. 709 Colour gamut
A "Rec. 709" is a badge a monitor is allowed to wear only if it is capable of displaying a certain amount of colours on the colour spectrum. Of all the colours the human eye can detect (shown as the patch of colours in the image), a monitor is "Rec. 709 compliant" if it can display all the colours shown inside the black triangle.
So if you see "Rec. 709" rest assured, all it means it. "This device can show THIS many colours"