What's the difference between VAR and _VAR_?

[Johnny Lee]

Hi,
   I'm new in python and I was wondering what's the difference between
the two code section below:

(I)
class TestResult:
	_pass_ = "pass"
	_fail_ = "fail"
	_exception_ = "exception"

(II)
class TestResult:
	pass = "pass"
	fail = "fail"
	exception = "exception"

   Thanks for your help.