Great ideas are not conceived by magic; they are typically the result of a process aimed exclusively at identifying, qualifying, and selecting the best ones for creating the product backlog and, subsequently, development.
Ideation is a creative process whereby new and innovative ideas are generated and captured. It typically involves sessions where brainstorming, sketching, and even quick prototyping (as is the case with hackathons) takes place. During the creative process, good ideas are shortlisted and should, in principle, become candidates for implementation, at which point planning takes place.