Barred sex linking, wherein the offspring are usually known as black sex links, are possible because barring in chickens is a sex linked gene. A basic explanation is that when you put a non barred rooster (and non white so you can see the head spot in the chick's down at hatch) over a barred hen, all the males will hatch single barred and will have a head spot, while the females will not be barred and not have a head spot. This works because a female always passes barring to her sons and never passes it to her daughters. A hen can only get barring from her father, and that's also why hens can only be single barred whereas males can be double barred and have two copies of the barring gene.
I could go deeper into this with an explanation of chicken chromosomes and how this works if you wanted. Unfortunately reading is the only way you'll understand the how of why it works, that part can't be learned just by doing
There are also red sex links, which you get when you cross a gold male to a silver female.