[R] What is the difference between expression and quote when used with eval()?

[blue sky]

I made the following example to see what are the difference between
expression and quote. But I don't see any difference when they are
used with eval()? Could somebody let me know what the difference is
between expression and quote?


expr=expression(2*3)
quo=quote(2*3)

eval(expr)
str(expr)
class(expr)
typeof(expr)
mode(expr)
attributes(expr)

eval(quo)
str(quo)
class(quo)
typeof(quo)
mode(quo)
attributes(quo)