A bankbook is a small book from the bank. Inside, staff write the money you put in, the money you take out, and the new total, so you can open it and see your account in one place. Another English name for the same thing is passbook. In some countries people now look at this on a phone instead, so the paper book feels old-fashioned there — though actually in Taiwan many people still bring a 存摺 to the counter to update it, so the idea is still very much alive. It is a plain money word, not slang. It is not a notebook you buy in a shop.

存摺