Texinfo provides four font commands that specify font changes in the
printed manual but have no effect in the Info file. @i
requests italic font (in some versions of TeX, a slanted font
is used), @b requests bold face, @t requests the
fixed-width, typewriter-style font used by @code, and @r requests a
roman font, which is the usual font in which text is printed. All
four commands apply to an argument that follows, surrounded by
braces.
Only the @r command has much use: in example programs, you
can use the @r command to convert code comments from the
fixed-width font to a roman font. This looks better in printed
output.
For example,
@lisp
(+ 2 2) ; @r{Add two plus two.}
@end lisp
produces
(+ 2 2) ; Add two plus two.
If possible, you should avoid using the other three font commands. If you need to use one, it probably indicates a gap in the Texinfo language.