Questions about the parameters in btManifoldPoint().

[Xuhai.Tang]

Hi, I have some questions about the parameters in btManifoldPoint().
what are the meanings of these following parameters in btManifoldPoint()
m_appliedImpulseLateral1(0.f),
m_appliedImpulseLateral2(0.f),
m_contactMotion1(0.f),
m_contactMotion2(0.f),
m_contactCFM1(0.f),
m_contactCFM2(0.f),
m_lifeTime(0)

Thank you in advance
Xuhai