A plain text file, plain text, plain text, plain text or bare text (plain English text) is composed only of plain text characters only, computer file which makes also human readable. These characters can be encoded in different ways depending on the language used. Some of the most widely used encryption systems are: ASCII, ISO-8859-1 or Latin-1 and UTF-8. Lack of information to generate formats (bold, underline, italics, size, etc.) and fonts (eg, Arial, Times, Courier, etc.). The term plaintext comes from a literal translation of the term plain text, a term which in Spanish means simple text or simple text.
RB is a container for holding Rocket eBook content. You can use DRM but books that came today not in use. The container typically contains an HTML file with images of the same and a pseudo-OPF (.info) file with all metadata or at least this is what it looks like after being converted.