Here's how it works (using the example of an English speaker learning French).
The first time you see a flashcard it will show you the French version, and ask you to guess the English translation. Since it's assumed you know English well, it seems pointless to type the English, and it's faster just to click to see the answer.
Hard directionAfter you've successfully remembered the meaning of the word, the next time it is shown, it will show you the English and ask you to guess or type (in typing mode) the French word or phrase. If you "Almost" remember, the card will be shown again later in hard mode. If you remember "Not at all" the card will fall back to easy mode the next time it is shown.
Passive ModeYou can force Readlang to only practice with in the easy direction by enabling Passive Mode in the Settings page.