The core idea
An auction is described as stopping through when the awarded yield is lower than the comparable pre-auction market yield.
What is happening underneath
It generally indicates stronger demand than the market had expected.
How investors should read it
Like a tail, it is most informative when considered with buyer participation and prevailing volatility.
The same market move can carry different information depending on which maturity, issuer and risk premium is changing. Read the question together with the underlying concepts rather than treating one price move as a universal signal.