There are two types of Partner Visas :
Prospective Marriage visa and Partner visa.
The type of relationship you are in dictates the type of visa you can apply.
1. If you intend to marry have a fiancé(e) but you are not yet married you will need to apply for a Prospective Marriage Visa.
2. If you are married and are in a de jure (legally married) relationship you will need to apply for a Partner Visa.
3. If you are in a de facto relationship you will need to apply for a Partner Visa.
If you are a spouse or a partner of a foreign country you should note that you do not have an automatic right to citizenship. You need to satisfy the eligibility criteria as other applicants to apply for the citizenship of that country.