It is often read as "entails", "models", "is a semantic consequence of" or "is stronger than".
, which has a single bar across the middle, and which denotes syntactic consequence (in contrast to semantic).
It has several different meanings in different contexts: In TeX, the turnstile symbols ⊨ and
In LaTeX there is the turnstile package, which issues this sign in many ways, including the double turnstile, and is capable of putting labels below or above it, in the correct places.
The article A Tool for Logicians is a tutorial on using this package.