Thunderbolt 1 & 2 used the Mini-DisplayPort connector. Thunderbolt 3 & 4 use the USB C connector. Thunderbolt is like external PCIE, you can connect a lot more than monitors with things like external GPUs being possible. You can use Thunderbolt 1&2 ports just as Mini-DisplayPorts too just like TB3&4 ports can be used just like USB C ports but they do more.
i saw more people using og thunderbolt for hard drives, capture cards, and audio interfaces than for displays. getting out of the split firewire ecosystem was a big deal
