PCIe Gen1 = 2.5Gb/s per lane, PCIe Gen2 = 5Gb/s per lane, PCIe Gen3 = 8Gb/s per lane
Gen 1 is often indicated as 1.0, Gen2 as 2.0 and Gen3 as 3.0
PCIe lanes are indicated by x1, x4, x8, and x16
Example: A PCIe x16 Gen3 board can operate up to 128Gb/s when inserted in a PCIe x16 Gen3 slot. 
Thunderbolt1 (TB1) has a 10Gb/s data path and a 10Gb/s Display Port
Thunderbolt2 (TB2) has a 20Gb/s data path and a 20Gb/s Display Port
A TB2 Board and a PCIe x4 Gen2 board can both operate up to 20Gb/s when installed in slots up to PCIe x4
An ExpressCard only operates at x1 Gen1 bandwidth so it operates at 2.4Gb/s