a small folded sheet of paper or card, usually with a picture on the front, inside which you write a short letter

a box of note cards 一盒邮简

a small piece of card or thick paper that you write notes on for speeches, school work, etc.

Put each question on a note card, with the answer on the back. 把每个问题写在一张记事卡片上，在背面写上答案。