This is a himalayan salt block. Check out good ones here (click me!)
My Aunt Laurie and Uncle Steven gave me this salt block for Christmas a few years ago. I didn't really have my own place and didn't really know what the hell it was. Then I woke up one night while watching my religion channel aka The Food Network and they were using a salt block to cook steaks. I looked at my friend and told her "Ya know, I have a salt block. Let's use it!" So we got some New York Strip steaks and did not marinate them whatsoever. You aren't supposed to use any extra salt because the salt cooks into whatever you cook on it.
That thing is about 450-500 degrees. I heated it up on the stove top (a few websites said it was ok) but now I heat it up in the oven because it is easier and not like watching water boil. It also cooks the food faster than you would expect - those steak strips were on there for about a minute or so on each side - MAYBE. You can cook anything on this - chicken, fish, shrimp, steak, veggies, eggs, sushi. It keeps the heat so you can take it out of the oven after it's been in there about an hour (be very careful, if it touches your skin you will say things rated-R), and I place it on a cookie sheet on my stove and cook stuff that way. If I feel it needs more heat, I take the block and put it back on the rack in the oven and let the food cook with all the awesomeness I can.
I recently realized it is way easier to clean the salt block with a wet wash cloth while it is still warm. This was after I cooked shrimp (maybe 1 minute a side) (I promise, extremely delicious).
This is my dog Carmen after a bath. Carmen looks a lot like a fox and a dingo. She's a huge fan of the salt block too. I saved her as a puppy from the local kill shelter. She likes raw tuna steaks, sticks, and chasing butterflies.