Here in this video we take a look at what is attribution modelling.
The video is quite basic but covers the basic aspects and also why attribution modelling is important.
Here we go more into the different models
And here is wikipedia’s definition of attribution modelling: https://en.wikipedia.org/wiki/Attribution_(marketing)
Though the definition there as of this writing is not entirely correct as also last-click is an attribution model so it does not necessarily have to be multi-touch.