System variable "$@" what is it in sh?

Shell Programming and Scripting
1

Is $@ a system variable? If so, what is it in bourne shell?

Thanks much,

John

2

Straight from the man page for sh
${parameter}
The value, if any, of the parameter is substituted.
The braces are required only when parameter is followed
by a letter, digit, or underscore that is not to be
interpreted as part of its name. If parameter is * or
@, all the positional parameters, starting with $1, are
substituted (separated by spaces). Parameter $0 is set
from argument zero when the shell is invoked.

Reading the man page for more info would be suggested.