Entailment

Informal:
Which formulas $B$ are true when $A$ is true?

Formal:
For all Assignments $\varphi$ which satisfy $A$, do these assignments also satisfy $B$ ?

$A$ entails/models $B$:

Entailment is the ideal outcome of reasoning.

Deduction is the process of an actual computer trying to reason about entailment.

Examples

Modus Ponens