It is a 1 x 3 array (a vector) of values that are datatype uint8 . uint8 datatype is an 8 bit unsigned integer, so each entry can represent values that are 0, 1, 2, 3, 4, ... 254, 255
The first entry in the vector represents the Red contribution. The second entry in the vector represents the Green contribution. The third entry in the vector represents the Blue contribution.
I do not know what the pixelcontrol is about, unless you are using the VisionHDL toolbox, https://www.mathworks.com/help/visionhdl/ug/pixelcontrol-bus.html in which case we would expect that the block is being used as part of a hardware (VHDL or FPGA) conversion from RGB to YCrCb -- though I do not seem to find a block for that purpose at the moment.
