Typically, a character set is a collection of graphical symbols, called Glyphs, which are used to communicate in a language. In order to represent the Glyphs in a computer, they must be associated with a numerical value, called a Code Point, for storage. In modern computers, the Code Points are stored in individual, 8-bit bytes of memory allowing 256 Glyphs to be represented. Relativity uses the term "character set" to refer to Glyphs and their associated Code Points.
On IBM PCs, the term "Code Page" is commonly used to describe this mapping of Glyphs to Code Points. However, on UNIX-based machines, it is more common to use the ISO 8859 standard to describe this mapping. Relativity provides character sets for both of these standards.
Relativity uses the character set of each file in order to interpret the Code Points stored within it. For example, if your data is in English and resides on Windows or DOS, selecting the character set for Code Page 437 would be appropriate. If your data is in English and resides on UNIX, the character set for ISO 8859-1 (otherwise known as Latin 1) would be appropriate.