The values identify the various host character sets that Host Integrator supports for 5250 and 3270 terminal emulation. The list varies slightly between 3270 and 5250 sessions.
Host Integrator uses this setting to choose a conversion table that it uses to convert host characters (EBCDIC) into PC characters (ANSI).
This setting should match the national character set used by your host system. If it doesn't match, then some characters, such as accents, may not display correctly.
See your host documentation for definitions of the characters in each set.