I don't understand when you use it and what the difference is between each other.
For example, when you say:
Depending on the context, they can all mean:
による modifies a noun, and both により and によって modify a verb or an adjective.
により and によって are almost synonymous, although in the informal context, によって is more usual than により.
I ended up reaching this post because I was looking for the answer while reading through the grammar but I think I finally understand.
Like user797 pointed out, によって is depending on/according to.
But whether or not you were asking this, I think want to know the difference from that compared to both による and によると. I'm assumign this because I was the most confused about this. The book I'm using specifically says that AによるとB means The information from 'B' depends on the actual source which is 'A'.
人によって意見は違う。 Opinions are different depending on the people. (no direct source) 彼によると悪い判断だった. According to him, it was a bad decision. (direct source is him)