Product Owner
The Product Owner is the bridge between software engineers, and the customers. She understands the technical side well enough, but most of all she is an expert in User Experience.
The usability of the product is always at the center of the Product Owners. Which features to prioritize, which experiments to perform, all originate in improving the user experience of using the product.
A great product manager has the brain of an engineer, the heart of a designer, and the speech of a diplomat. – Deep Nishar
Skills
Managing stakeholders
With so many points of contact, it is an art to balance the interests of different stakeholders without compromising the end result.
Diplomacy
The Product Owner depends on engineering, on sales, and on the users, and probably has KPIs overlapping with this areas. They cannot be an authoritarian figure, but diplomatically make reasonable choices that satisfy all the parts involved. Most of all, the user.