Can I have an animation that is variable at runtime?

My specific situation: I have a club or some weapon which the player can swing. Depending on where the player taps / clicks that will be the target of the club swinging. At rest, the club returns to the same position. So I suppose I need the destination of the animation to be where the player tapped.

Is this possible and how?

(side question - I see a lot of talk about Mecanim, but when I search online I don’t actually get any information about what it actually is, how I get it and how to use it.)

Thanks in advance!

Mecanim is the name for the built-in animation system inside Unity (just like Enlighten is the name for the lighting system). If you use an Animator component then you are using Mecanim. I suggest you start by going through the animation tutorials here.

On a more specific note about your question: You should check out the UFPS asset which uses realtime-generated motion.