This version of the app is free and has no ads, however not all courses are complete. If you want full access to the Kanji Study content (which is immense) you need to purchase the full version via the app.
Kanji Study enables you to see the correct drawing of each kanji, as well as examples showing how they are used. You can also study using cards, in addition to participating in a type of test exam. Either way, all of these tools are designed for users who have some previous knowledge of Japanese. In other words, they are not for people who are starting from scratch; rather those who already have a base to work from.
Kanji Study is a great app for studying Japanese, allowing you to genuinely improve your Japanese knowledge. All you need is time and the will to do so.