Mainboard is out due to water entry
Motherboard over head
The main board is a circuit board where various electronic components are interconnected like on a PC or Macintosh and commonly abbreviated with the word mobo.
Another notion of a motherboard or mainboard is the main board of pcb which has a bios chip (drive program), paths and connectors connecting each access device. Because the motherboard is all the components of the PC will be unified.
The motherboard connects all the computer equipment and makes it work together so that the computer can run smoothly. Inside the motherboard itself there are parts with each function. Here's the inside of the motherboard: