The 644753-3 is a 3-position, single-row, vertical through-hole header from TE's MTA-156 series, designed for board-to-cable/wire applications. The shrouded single wall gives some polarization protection during mating. Current rating varies by wire gauge; for the MTA-156 system, typical per-contact current is around 5A with 18 AWG wire, but always check the terminal derating curve for your specific wire size.
The 0.425" (10.80mm) insulation height gives clearance above the board for the receptacle to seat fully.