Pin header and female header are also called board-to-board, but in the market, small pitches such as 0.3mm, 0.4mm, 0.5mm are called board-to-board, and the larger pitches are 0.8mm, 1.0mm, 1.27mm, 2.0mm, 2.54mm. They are called pin headers and females to distinguish them. Regardless of the pin header and the board to the board, they are actually board-to-board connectors. One board is welded with pin headers, and the other is welded with headers. First of all, the height of the two boards is limited before the pin headers are needed to connect. In addition, the male and female mating facilitates the separation of the two boards, and also facilitates reverse repair. Secondly, the space of the circuit board is limited nowadays, and the pin header is used to save space.