What is public const epsilon

What is Public Const Epsilon = 0.0000000005 in constants.vb module?

(1) What is this function used for?

Public Function IsZero(x As Double) As Boolean

Return Math.Abs(x) < Zero

End Function

(2) Whis is this function used for?

Public Function ChainRule(ByVal f As Evaluable, ByVal g As Evaluable) As Evaluable

Return New Operation(Op.Times,f,g.Derivative).Simplify

End Function

(3) What does an underscore prefix mean?

What is public function compareto really do? (in DataPoint class)?

What does mustoverride stand for? What is different between override and mustoverride?

(4) What does enum stand for?

In statement “MyEvaluable = eva.Clone”, what does the clone attribute mean?

In statement “MyEvaluable.Simplify, what simplify stands for throughout the program?

What does the GraphingData routine do?

Is the entire Operation and ValueObject used by expressions specified in general expression screen?