Originally Posted by man ksh

`command`

The shell will expand the command substitution by executing
command in a subshell environment and replacing the command
substitution (the text of command plus the enclosing $() or
backquotes) with the standard output of the command, remov-
ing sequences of one or more newline characters at the end
of the substitution. Embedded newline characters before the
end of the output will not be removed; however, they may be
treated as field delimiters and eliminated during field
splitting, depending on the value of IFS and quoting that is
in effect.