As defined in Scrum, the scrum team comprises of the development team, the scrum master and the product owner, so yes, the product owner is a CRUCIAL part of the scrum team. The product attends the scrum ceremonies with the development team and stays available throughout the sprint to assist the team members in terms of requirements. The product owner is part of the sprint planning to ensure the team commits the right work and also which adds value to the product. Throughout the sprint, the product owner may or may not join the daily scrum but will be there to assist.

During the sprint demo, the product owner has to be there to accept/reject the work done during the sprint and also to provide feedback on the deliverables. The team ALONG with the product owner also sits together for the BACKLOG grooming where they brainstorm on the requirements and make it ready to be pulled up for commitment in the upcoming sprints. It is the product owner who acts as a bridge between the delivery teams and the client hence, it is an important ROLE in the scrum team. Though this role might not be involved in the technical part they take care of the functional aspect.