The .bin file extension denotes a binary file. This generic term essentially encompasses files that contain bit patterns and are therefore not not composed or not exclusively of printable characters. This distinguishes them from regular text files, and explains why opening .bin files with a text editor presents difficulties. If you still want to try, you will notice that the program will return partially or completely unreadable strings.
Binary files are basically used to optimally store precise data fields and prepare them for computer processing. Applications that can be run directly are also often stored as a .bin file.