A flashcard is a card which is used as a memory and learning aid. One side of the card will contain information of one sort, a word or a picture, and the other will have the information one wants to memorise or learn.
For example, one side could have a word in L1 or a pictogram and the other side the word in English. It can be used for individual words or for prompting whole sentences. Although frequently used in language learning they are not limited to this use.