The first video goes over all of the central parts and keys of the Lumia 950. It's pretty dry concerning narration and presentation, but it does a solid job in presenting all of main hardware features of the phone, along with a couple of tips on how to use them
The second video is more of a "how-to" video as it goes over the procedure for inserting a new SIM card and memory card inside the Lumia 950. This video will likely be more important if you decide to purchase an unlocked version of the phone.
Thanks to Mark for the tip!
Source: Lumia Support (YouTube)