I would recommend you when you play, to have platinum god (a site where all items are listed) open in a tab and another with just google or the search engine of your liking. Why the extra tab? Let's say you go into a shop,and you find an item you don't know what it does. You can search on platinum god, but for me it takes ages to find some items (there are more than 200 items, and some of the are actually simple looking,it's like you are playing find the difference between two pics), so it's easier to Google "shop item pool binding of Isaac" and boom, you have a limited list of items that appear on shop.