Why does that matter? PCIe is the protocol inside your computer that connects the CPU to a graphics card, SSD, or RAM. By routing PCIe outside the computer, Thunderbolt effectively turns the outside world into the inside of your PC.
With Thunderbolt 3 and 4 (and the new 5), you aren't just moving files; you are opening a direct expressway to your computer’s brain. That is how you can plug in an external GPU (eGPU)—a massive desktop graphics card—into a lightweight ultrabook and suddenly play Cyberpunk 2077. The port isn't just moving data; it is expanding the computer's architecture. The real turning point was the adoption of the USB-C connector with Thunderbolt 3. This was a brilliant piece of branding and engineering. Physically, a Thunderbolt 3 port looks exactly like a USB-C port. This caused initial confusion (is it a charging port? a display port?) but ultimately led to victory. Thunderbolt
For the better part of a decade, the average laptop user lived in a dongle hell. You had a power cable, a USB-A for your mouse, an HDMI for a second screen, an Ethernet dongle for stability, and maybe a proprietary slot for an SD card. It was a mess of spaghetti logic. Why does that matter