What's the difference between parenthesis $() and curly bracket ${} syntax in Makefile?

Question

Is there any differences in invoking variables with syntax ${var} and $(var)? For instance, in the way the variable will be expanded or anything?

Answer 1

Actually, it seems to be fairly different:

, = ,
list = a,b,c
$(info $(subst $(,),-,$(list))_EOL)
$(info $(subst ${,},-,$(list))_EOL)

outputs

a-b-c_EOL
md/init-profile.md:4: *** unterminated variable reference. Stop.

But so far I only found this difference when the variable name into ${...} contains itself a comma. I first thought ${...} was expanding the comma not as part as the value, but it turns out i'm not able to hack it this way. I still don't understand this... If anyone had an explanation, I'd be happy to know !