Learning with flashcards is one of the most popular and efficient learning methods and works very easily. You will need a card index box with five increasingly large subjects and the index cards. Write the question on the front of each card and the answer on the back. When learning English vocabulary you write the German word on the front and the English translation on the back. You can also learn vocabulary in reverse order, from foreign language to native language.
In principle you can learn with index cards everything what can be represented in the form of question and solution.
Mostly index cards are used for learning vocabulary, because they are excellent for that.
But also definitions, chemical formulas, terms from all subject areas and very specific facts can be imprinted very easily and effectively with flashcards.
The first learning step already starts when you create the flashcards, when you have to deal with the question and the solution.