Mandarin is a spoken form of Chinese. So Mandarin and Cantonese, for example, share the same character set (Chinese). There's also traditional vs simplified Chinese, technically; they're similar with some differences in how they're written. Japanese also has some differences which can be confusing because a lot of application developers just use the Chinese character sets for kanji: https://heistak.github.io/your-code-displays-japanese-wrong/
One other thing about Chinese is that TV shows and movies usually have hard-coded subtitles while airing because the spoken versions of the language can be very different from one another. Including the text makes it more accessible to a wider audience regardless of what "dialect" is spoken in the show.