The Akashic Records are believed to be the total library of everything that is known, and everything that is going to ever be known. They are said to exist on the non-physical astral plane. All accounts as of yet are anecdotal, with no scientific evidence confirming their existence.
H.P. Blavatsky(1831-1891) is said to have introduced the term akasha to the theosophy codex. She described them as being a sort of life force. Blavatsky stated that the “indestructible tablets of the astral light” contained all human thought and actions of the past and future. Blavatsky however, did not use the term “akashic”. The term akashic record is a term attributed to Alfred Percy Smith. Smith wrote Esoteric Buddhism (1984), and in that book he said there is a Buddhist belief in a “permanency of records in the Akasa” and “the potential capacity of man to read the same”. Another occult author by the name of C.W. Leadbeater , in his book Clairvoyance (1899) wrote that a clairvoyant would be able to read the akashic records.
Here is a link to one method of accessing the akashic records.
Here are a few books on the subject if you wish to expand your knowledge.