[r] What is the difference between a Contracting State and a State Party to a Convention?

The Vienna Convention on the Law of Treaties of 23 May 1969 gives the followings descriptions:

Article 2 - Use of terms
1. For the purposes of the present Convention:
(...)
(f) 'contracting State' means a State which has consented to be bound by the treaty, whether or not the treaty has entered into force;
(g) 'party' means a State which has consented to be bound by the treaty and for which the treaty is in force;
(...)