I just like flat ciders really sweet or dry I was just under the impression I needed tannin not sure what it does or anything lol
Tannins add dimension. Think about fruit that you have eaten in the past. Ever bite into an unripe piece of fruit and get a bitter or sharp flavor that makes you pucker? Or have you ever had sip of wine And your mouth/tongue feels like sandpaper? Those are tannins and acids.
Some apples are great for eating, others for baking or jam. The baking aoples are more bitter,sharp,sour whereas the eating apples are more sweet. Some of this is variable due to the ripeness of the fruit as well as how long the juice is left in contact with the skins and stems/seeds.
Apple juice that you buy from the grocery store is targeted for a drinking profile, not a fermentation profile. You can make cider with regular store juice, but the end result lacks complexity of a great cider. Making cider from these juices is kind of like making light beer.
But don't worry, many of us make darn good cider with store bought juice. There are things you can do to make your cider better.
Watch out for cheap juice, check That there are no preservatives other than vitamins C/ascorbic acid.
Watch for sugar additions, especially off brand from concentrate. Can be used, but sugar will add abv but no residual flavors.
Some, like myself,
@Maylar and
@Blacksmith1 (I think) stabilize and back sweeten with apple or other juices.
Some do acid and tannin adjustments to add body and flavor.
Temp controlled fermentation, appropriate nutrients.
Read through the forums, ask questions. Lots of good info here.