threshold, performance materiality and materiality

I would appreciate if friends would contribute to interrelation among threshold, performance materiality and materiality. Lets assume we are an external audit team engaged in auditing of any company (eg manufacturing, banking or whatever). On which stage of engagement we will calculate threshold, performance materiality and materiality and how we assume to benefit from this information. Among these definitions, least of all I understand is threshold. I would appreciate your presence in the forum. Thanks