What is the difference between a PCIe x16 slot and an express card

What is the difference between a PCIe x16 slot and an express card pcie slot height The Riser from Dell™ fits into the PCI-E slot of your Dell System Riser cards are used to extend a slot for a chip or card in a fully loaded computer pcie slot x16 The next-gen interface standard A reinforced PCIe slot on Aorus Pro Z690 motherboard PCIe or Gen 5 is

pcie slot x16 PCIe Slots · A PCIe slot that supports a full-height full-length PCIe card also supports a full-height half-length or half-height half-length

pcie x 16 slot The Riser from Dell™ fits into the PCI-E slot of your Dell System Riser cards are used to extend a slot for a chip or card in a fully loaded computer  PCIe riser 2slot 2 Includes PCIe cable connectors for front-loading NVMe SSDs 12 Supercap unit mounting bracket (RAID