Digital Cinema Initiatives - Protocol 3 is known as DCI-P3.
It is a color scheme created by the Society of Motion Picture and Television Engineers (SMPTE) and Digital Cinema Initiatives (DCI) to standardize the colors used in the film and television industries.
A version of the DCI-P3 color space known as DCI-P3-D65 is also used by high-end PC monitors, TVs, and smartphone displays; however, you'll typically see this written as DCI-P3.
When purchasing a PC monitor, TV, or other device, the vendor may state that the item offers a particular proportion of DCI-P3 or P3 color space. The monitor can reproduce as much of the DCI-P3 space as shown here, though it needs to be tested to determine whether it does so accurately.
True DCI-P3 is aimed at what you see in theaters because this is a DCI standard. In home products, you'll typically find DCI-P3-D65, but, once more, it's almost always listed as DCI-P3, leaving out the D65 part. The difference between true DCI-P3 and DCI-P3-D65 is in the white. Due to its preference for projection systems, true DCI-P3 has a greener white.
As most 4K and even 8K monitors typically include the color wheel over the marginally outmoded sRGB color spectrum, DCI-P3 is particularly well suited for contemporary ultra-HD visuals.
DCI-P3 is undoubtedly preferable to sRGB if you want to fully enjoy HDR, and the more DCI-P3 coverage there is, the better. You can then take advantage of the additional colors that HDR content can have.