M:
Lobe
Seperation
Angle is simply a measurement of the angle, formed from the centerlines of the intake lobe and the exhaust lobe, measured in degrees of cam rotation. [FYI, LCA is measured in degrees of crankshaft rotation.]
Just imagine 2 imaginary lines, one extending from the centerline of the intake lobe, the other extending from the centerline of the exhaust lobe. The amount of camshaft rotation (in degrees) that it takes for the centerlines to pass the same specified point is the LSA.
So, a "tight" angle, or smaller LSA (normally 100-112) will have MORE valve overlap, meaning a lopey idle, poor vacuum quality, and the torque peak will move up the rpm range...think "top end" cam. Likewise, a "wider" LSA (112-120) will have less overlap, thus trapping more of the charge in the cylinder at low engine speeds, and will provide a better vacuum signal, and have a tame "lope" to it's idle...think "low or mid range" cam.
But, as Sam eluded to above, their are a few other "variables" provided by the cam that can influence how a cam reacts.