as others have already said Logic Board is the other commonly used term. I've heard Apple refer to it as the MLB or Main Logic Board, too.
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the term motherboard originates from early days of computers where the motherboard contained the CPU and other major logic, and usually also expansion slots. You could plug "daughterboards" into those slots to expand the functionality of the computer - e.g. printer interface, sound card, graphics card etc.
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the term motherboard originates from early days of computers where the main circuit board contained the CPU and other major "logic" or chips, and usually also expansion slots. You could plug "daughterboards" into those slots to expand the functionality of the computer - e.g. printer interface, sound card, graphics card etc. That was a distinguishing feature of a motherboard.
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p.s. to get into even more background of the terminology, the "board" part of this comes from the general term Printed Circuit Board, or PCB. this is the physical, non-conductive board on which there are conductive traces connecting the various electronic components. Logic board is just another way of referring to the PCB containing the major "logic" or chips of the computer.
as others have already said Logic Board is the other commonly used term. I've heard Apple refer to it as the MLB or Main Logic Board, too.
the term motherboard originates from early days of computers where the motherboard contained the CPU and other major logic, and usually also expansion slots. You could plug "daughterboards" into those slots to expand the functionality of the computer - e.g. printer interface, sound card, graphics card etc.