As the most simplified answer, you can substitute whatever is on the left-hand side of => with the word "LEFT" and whatever is on the right-hand side with the word "RIGHT".
Then, the meaning of "LEFT => RIGHT" becomes:
Take LEFT then do RIGHT.
This means that if you have a "()=>" that you can take nothing (that is, no parameters) and then do whatever is on the right-hand side.
This is the most common meaning.
