Packed pixel

In packed pixel or chunky framebuffer organization, the bits defining each pixel are grouped together. For example, if there are 16 bits per pixel, each pixel is represented in two consecutive (contiguous) 8-bit bytes in the framebuffer (a.k.a. screen buffer). If there are 4 bits per pixel (16 colors), each frame buffer byte defines two pixels, one in each nibble. The latter example is as opposed to storing perhaps half of the bits—2 bits—for each of four pixels in one byte and the other two bits for each of those four pixels in another byte or bytes. It is also as opposed to interleaving the bits of the two pixels within the byte. As this illustrates, packed pixel organization can be directly contrasted with planar organization.

...
Wikipedia