The Project Sponsor is the Project Owner, they're both the same role. I have noticed that the use of the term Project Owner is mostly common in the UK. In most other countries, the term Project Sponsor is used.
Since you work in a multi-national country, that might be the reason why you hear both terms.
Note that the Project Sponsor/Project Owner is also a Project Stakeholder (but not the other way around, a project stakeholder is not necessarily a project sponsor). This is basic but I've seen this confused so many times that I thought I had to mention this remark.