A normal extension cord like we've all used has a plug at one end and a socket at the other, so you won't get killed by simply mishandling it.
I love this part of the product description:
"It Can Help Protect Your Family And Keep Them Safe"
Right...
Having said that, the longer Product Description With Every Word Capitalized explains the use case somewhat:
You've lost power and it will be likely be out for quite some time. But you had the foresight to have a generator and one of these cords. You plug one end into your generator and the other end into an ordinary wall outlet. Now every outlet on that circuit will be powered from your generator.
However, your normal fuse or circuit breaker will not protect you from an overload on that circuit, because you've just hotwired your generator into the "house" side of the circuit. So, as the description says, you may be able to power your refrigerator and some lights, but overload the circuit and you may burn your house down.
Also be sure to turn off that breaker or remove the fuse on that circuit. Otherwise you will be having some fun when power is restored!
Oh gosh, it gets even better. Check out the reviews on the Amazon listing!
Finally, I would like to thank the parent commenter for asking an honest question. Perhaps it sounded naive to some, but I appreciate a question like that, as it gave several of us a chance to explain the issues around this kind of electrical cord.