What's the difference between Parameter speed and angularspeed?

I changed my character model and managed to make animations from the old model work with the new model but I have one strange behaviour. When I use in the animator as parameter angularspeed then my new model makes strange movements when I keep the up-key pressed and then press the left keep. Apart from the strange headmovement it reacts to this key combination.

When I change the parameter to speed in the inspector then this strange head moving is gone but the model reacts only to the left key when I don't press the up-key during the walking.

What's the difference between these 2 parameters and why does it cause a different reaction to the key pressing?