This is a game which trains the visual cortex in your brain to recognize the shapes of the kanji, and teaches you their basic meanings.
It does not teach you to read the kanji, that involves a completely different part of your brain, and there's a separate game for that.
Kanji are not words. It is very important to understand this because words are spoken, whereas kanji are not. You should learn the meaning(s) of the kanji first, then learn to read words which contain them. Trying to learn the readings first is a very bad idea for a number of reasons:
Consider the kanji: 日 (day, sun), which is one of the very first ones you learn. It can be read as "hi", "bi", or "nichi", depending on the context. However, it can also be present in a word without affecting the reading at all! For example, the Japanese word for "today" consists of two kanji, the first meaning "now", and the second meaning "day".
今日 (today) = "kyō"
The interesting thing is that neither of these kanji affect the sound of the word at all; they only provide meaning. If you know the meanings of the kanji, you'll have a good chance of understanding the gist of a sentence, even if you can't read it aloud correctly.
Your brain is fantastically good at recognizing and remembering shapes. This game is designed to leverage that power to provide a gentle introduction to learning kanji.
The game is multiple choice, making it easy to play one-handed while on your commute, etc. It shows you a kanji, then gives you four options to chose from. If you know the answer, then that's great! Just tap the correct option and the game progresses to the next question.
If you don't know the answer, then you have two choices how to proceed. Either way is equally valid, it's just a question of your personal preference:
When you're first getting to know the kanji, it's okay to take a few seconds to inspect them visually. But the more you have to think about it, the more you're using the cognitive part of your brain, which is the wrong bit. Ideally, you should play this game until you can recognize the kanji at a glance, without having to think about it at all.