A distributed system is one that has multiple interacting components or microservices. These components may be owned and managed by different entities or a single entity. When they are managed by a single entity, it would be a distributed system that is centralized in ownership/control (e.g, Google search, facebook are distributed systems that are centrally owned). Of course, a centralized system may have just one component, in which case it won’t be a distributed system.
When a distributed system is owned and controlled by different entities, it is also referred to as a decentralized system. All or many of the nodes in the system partake in the decision making process. So, by definition, all decentralized systems are distributed systems. A good example is BitTorrent. A blockchain is also a decentralized system.