What is the difference between . (dot) and $ (dollar sign)?

Question

What is the difference between the dot (.) and the dollar sign ($)?

As I understand it, they are both syntactic sugar for not needing to us

Answer 1

My rule is simple (I'm beginner too):

• do not use . if you want to pass the parameter (call the function), and
• do not use $ if there is no parameter yet (compose a function)

That is

show $ head [1, 2]

but never:

show . head [1, 2]