Just look at the Wikipedia article to get your definition:
Tacit programming (point-free programming) is a programming paradigm in which a function definition does not include information regarding its arguments, using combinators and function composition [...] instead of variables.
Conventional (you specify the arguments explicitly):
sum (x:xs) = x + (sum xs) sum  = 0
sum doesn't have any explicit arguments - it's just a fold with
+ starting with 0):
sum = foldr (+) 0
Or even simpler: Instead of
g(x) = f(x), you could just write
g = f.
So yes: It's closely related to currying (or operations like function composition).