It's taken over the gourmet world. You pretty much wouldn't write a recipe that includes salt without it. It's also an annoying fact of life for those of us googling "kosher" recipes - that yummy salt bumps up almost every recipe to the top of the list even if it's a recipe for bacon double cheeseburgers.
First of all, you may already know that "kosher" salt is no more or less kosher than any other salt. That is, it's kosher, but so is table salt, coarse salt, sea salt, Himalayan pink mountain salt, and every other form of pure salt.
So if you eat kosher and cook kosher, you CAN use kosher salt. But you don’t have to.
So why is it called kosher?
That’s actually just a mistake. This flattish crystalline form of salt is actually kosher-ING salt - the kind of salt used to "kasher" meat to make it kosher.
Most kosher salt has air between relatively flat crystals. So when you're using or substituting kosher salt, use "more" of it - the same amount by weight looks like more on a spoon, so 2 tsp of regular table salt will be just as salty as 1 tbsp or more of kosher salt. Many people claim it has a “lighter” flavour, but in reality, it tastes the same as any other salt – you’re just using less of it.
Here’s a picture showing a comparison between different types of salt, close-up: