help me to understand cams

The biggest problem with cam theory is they are the heart of the engine, and an engine is very individualistic. You can have two 408s, with every part exactly the same, but have different cams, and they will be totally different personalities. Conversly you can have the exact same camshaft in a 360, and a 408, and again - they will be entirely different.
In terms of "short and sweet" hints...
The longer the stroke, and the higher the static compression ratio, the smoother the idle and lower rpms the power will occur at for any given camshaft.
The wider the Lobe Seperation Angle, and/or the higher numerically the Intake Center Line, the smoother the idle and the flatter the power peaks will be.
A solid flat tappet cam and a hydraulic flat tappet cam that are "identical" on paper are not identical and the hydraulic will have the more raspy idle and a more peaky power curves.