A character encoding is a mapping from a set of characters to their on-disk representation. Jalatext can use any encoding supported by the Java platform.
Note that there is no general way to auto-detect the encoding used by a file, however Jalatext tries to auto-detect it. If there is some character that is not viewed correctly, you can change the encoding used to interpretated the file selecting View->Change current encoding.
While the world is slowly converging on UTF-8 and UTF-16 encodings for storing text, a wide range of older encodings are still in widespread use and Java supports most of them.
The simplest character encoding still in use is ASCII (American Standard Code for Information Interchange). ASCII encodes Latin letters used in English, in addition to numbers and a range of punctuation characters. Each ASCII character consists of 7 bits, there is a limit of 128 distinct characters, which makes it unsuitable for anything other than English text. Jalatext will load files as ASCII if the US-ASCII encoding is used.
Because ASCII is unsuitable for international use, most operating systems use an 8-bit extension of ASCII, with the first 128 values mapped to the ASCII characters, and the rest used to encode accents, umlauts, and various more esoteric used typographical marks. The three major operating systems all extend ASCII in a different way. Files written by Macintosh programs can be read using the MacRoman encoding; Windows text files are usually stored as windows-1252. In the Unix world, the ISO-8859-15 character encoding has found widespread usage.
Many common cross-platform international character sets are also supported; KOI8_R for Russian text, Big5 and GBK for Chinese, and SJIS for Japanese.