The "MP" is the Management Module, we also refer to this as the MM. The "LP" is the Line Card, these are your port modules that house your ethernet interfaces. There are many types of LPs; 10Gbps, 40Gbps and 100Gbs, all with their own different varieties of capacity; 8x10G, 20x10G, 4x40G, 2x100G etc.
I hope that clears things up for you,
Michael Morey Principal Technical Support Engineer / Extreme Networks Advance How We Connect by Challenging Complexity
Michael Morey Principal Technical Support Engineer Extreme Networks