Text encoding is a tricky thing.
Years ago, there were hundreds of different text encodings in an attempt to support all languages and character sets.
Nowadays all these different languages can be encoded in unicode UTF-8, but unfortunately all the files from years ago still exist, and some stubborn countries still use old text encodings.
Many devices have trouble displaying text encodings that are not UTF-8, they will display the text as random, unreadable characters.
This tool converts the uploaded text files to UTF-8 so modern devices can properly read them. You can uploaded multiple files at the same time, or upload a zip file.
If VLC media player doesn't show subtitles correctly even after using this tool, then you have to change the font VLC uses. Here is a guide to fixing subtitles in VLC.
All the other tools on this website automatically detect text encoding and return their output in UTF-8. When using this website, you don't have to worry about text encoding.