is sherry cooking wine the same as sherry wine? I'm using it in a cake recipe...
Noooo! 'cooking wine' is not something one should cook with, or do anything else with. The general rule is to not cook with it if you wouldn't drink it.
Cooking sherry is basically not very good quality sherry, and I believe it has some salt added. It can work okay in sauces and such, but anywhere the sherry contributes important flavor it's generally a better bet to use regular sherry of slightly higher quality. I would hesitate to use cooking sherry in a cake recipe, especially because of the salt thing. Another to know about sherry is that it comes in cream sherry or dry sherry, which are very different from each other (cream sherry is quite sweet). Though in cooking, usually if it doesn't specify, the recipe means dry sherry.
A cake with sherry sounds awfully delicious!
Supermarket sherry cooking wine is diabolical. Real Spanish sherry (Jerez) is delicious on its own. And avoid the California produced "green bottle" sherries. It really is an AOC Spanish product in the same way that there is no such thing as California "champagne".
Buy a fairly decent, drinkable dry sherry to use in baking and cooking. No need to buy something terribly expensive, but it should be something that would be pleasant to drink.
I try never to say "never," but I would do whatever is necessary to avoid any wine, Sherry or otherwise, that is labeled "cooking wine." To a one, they are poor quality wines that couldn't be marketed any other way, and lots of salt is added. If you compare the cost of a full-sized bottle of real Sherry (retail usually under $10) with the price of the teeny bottles sold on the supermarket shelves of "cooking wine," you will also see how expensive they are for what you are getting.
Besides, you can drink the real stuff, if you want to.
Additionally, Sherry is a fortified wine, and keeps well on a pantry shelf for a long time -- ass opposed to "regular" wine which, once opened, has a shelf life of only a couple of days at best.