What are PCIe Slots in PC?

I'm actually a little more concerned over the dent in the circuit board causing the board not to fit in the slot Pin B65

A part had fell out and I thought I had broken my graphics card for sure, but it did not fit the GPU nor it looked like the card was damaged, a

broken slot machine RAM components are either soldered directly to the motherboard or inserted into a slot on the motherboard

broken pcie slot Slot 2 has an Avermedia card, and that is recognised in device manager and the BIOS Slot 3 is empty I have tried the original ATI Radeon but