APP is essentially a computer software, but it runs on the mobile phone platform. Therefore, as a software, APP can be protected by copyright at first, which is regulated by the Regulations on the Protection of Computer Software. Copyright shall be enjoyed from the date of completion of development, but in order to facilitate the exercise of rights and objectively prove the date of completion of development, it is suggested to apply for copyright registration of computer software after completion of development.
At the same time, if the pictures and music used in the APP can constitute works in the sense of copyright law, these pictures, music and words are also protected by copyright law alone.
Special case: if an APP is novel and creative, it can solve technical problems, and it is also possible to obtain an invention patent and be protected by patent law. However, this point is still controversial at present, and most software cannot be patented.
The original answer is from the seasonal romantic ocean.