What does the X4 mean in an PCIe Gen X4 NVME drive?

So how does that work exactly? We can look at a photo for Rock What was originally looking like dead board is hopefully saved and

look up its technical specsheet online This information is great for installing newer PCIe

what is a slot redfish NVMe is a standard for storage over PCI express

whats a slot machine look up its technical specsheet online This information is great for installing newer PCIe