The 1-746610-7: The feed-through feature lets you daisy-chain the ribbon cable through the header to another connector down the line — handy for bus-style signal distribution inside an enclosure.
This header accepts 26-28 AWG stranded wire or 26-30 AWG solid wire in the IDC slot. The 0.050" (1.27 mm) cable pitch matches standard rainbow ribbon cable, so you can mass-terminate a whole cable assembly in one press stroke.
That's a heavy tin layer — well above the flash plating you see on low-cost headers — which gives decent wear resistance for the moderate number of insertion cycles this DIP header typically sees in a production harness or field-service swap. Tin is fine for signal-level currents in dry-circuit or low-voltage applications; if you need gold for corrosive environments or high-cycle reconnect duty, the AMP-Latch series also offers gold-plated variants, but this part is built for standard indoor equipment.