Most of what a person knows — the sound of their laugh, the reason behind a decision, the story they only told once — disappears within a generation or two. Not because it did not matter, but because no one wrote it down.
A legacy is simply refusing to let that happen. It is a grandchild, not yet born, one day hearing their great-grandparent describe the day they emigrated, or reading a letter in their own hand.
You do not need to capture everything. A handful of stories, a few photographs with the names filled in, one recorded message — that is already a gift no future family member could give themselves.