Other Memory is the term used by the Bene Gesserit Sisterhood to describe the well of genetic memory their Reverend Mothers possessed. Non-Bene-Gesserit users of Other Memory include Paul Atreides, Alia Atreides, Ghanima Atreides, Leto Atreides II, Siona Atreides, and the final ghola of Duncan Idaho (via the unlocked memories of all of his past lives).
Other Memory was used mainly as a source of knowledge, especially when much written history had been lost to time. It was only made available to an individual after they successfully converted a Awareness spectrum narcotic. If they could not, they died.