The phrase “... a tale, told bye an idiot” refers to life. Macbeth after being told of his wife’s death, he says:
Life is but a walking shadow, a poor player
That struts and frets his hour upon the stage
And then is heard no more. It is a tale
Told by an idiot, full of sound and fury
Signifying nothing.
In other words, life is nothing but meaningless due to the facts that it isnt that long.