DCI-P3 is a color standard used in digital cinema. It shows a wider range of colors than the standard sRGB, especially in reds and greens.
Most modern 4K HDR TVs support DCI-P3, which means movies look closer to how directors intended in theaters.
For example, in nature documentaries, leaves and landscapes look more vibrant compared to TVs limited to sRGB.
See also: Wide Color Gamut (WCG), Adobe RGB, Color Gamut