The Yealink WH64 and WH64 Hybrid are identical headsets. The main difference is the WH64 Hybrid doesn't include a charging base for connectivity with a desk phone (there's a charging stand you can get for charging, just not for desk phone connection). The WH64 Hybrid includes the WDD60 USB Dongle and is best made for your computer and mobile phone.
Whereas the Yealink WH64 includes a charging stand that allows for connetivity with a corded desk phone (like Poly, Yealink, Cisco etc..) The WH64 also gives you the ability to connect with a computer and mobile phone as well.
If you're someone that uses a headset in the office with a corded desk phone, but you'd also like to use the WH64 on the go with a laptop, you could get the best of both worlds by getting the Yealink WH64, then add the WDD60 USB Dongle and you'll have an all in one wireless headset for in the office and on the go with your laptop/mobile phone.