What is Stories We Tell? Writer/Director/Focal Point Sarah Polley suggests that it's an exploration of memory and the discrepancies that can result from the telling of a single tale. Her father suggests that maybe the documentary is a way to come to terms with her mother Diane, a woman whom Sarah never fully understood. Considering the focus on her mother, maybe it's Polley's portrait of a fascinating woman who defies simple categorization. At different times, it's all of these things, but it's populated with a group of people whose apparent openness and warmth prevents the film from being overwhelmed by higher concepts.
Throughout the film, Polley continually says (and her interviewees believe) that her work is about exploring the differing perspectives that contribute to a variety of takes on single series of events. This may be the initial purpose, and to some extent, Polley accomplishes this as we see her family and their friends disagreeing on minor points during the course of the film. However, this is far from Rashomon. The different stories - while varying in some details - add up to a single narrative that all participants agree on. So, while the aspects of disagreement make for a few fun moments as family members squabble over who said what when, they don't really add up to much of a commentary on memory or storytelling.