Macroblock

What Does Macroblock Mean?

A macroblock is a processing unit in visuals and
video compression, and is based on linear block revamping. This is
then subdivided into transform blocks and it is further subdivided into
prediction blocks.
A macroblock is usually a block of adjacent pixels,
typically 16×16.

Techopedia Explains Macroblock

Standalone
frames in a picture are called I-frames. These are divided into 8×8
blocks that are not overlapping by nature. These are called pixels.
These pixels are then further rearranged into 16×16 blocks called
macroblocks. Any macroblock consists of a 16×16 array of luma. These
elements consist of 16×16 luma samples, and 8×8 chroma samples. Luma samples denote the brightness or the
achromatic portions, while the chroma samples denote the chromatic or the
colored portions. Thus, macroblocks can be thought of as 16×16 pixel
areas. The JPEG image format is based on macroblocks.