its about pragmatics

1. Implicature & Entailment

2. If inference is what listeners do to interpret the
meaning of utterances, implicature is the
process through which speakers include meaning
beyond the literal message in an utterance.

3. Bob: Are you coming to the party?
Jane: You know, I'm really busy.

4. Entailment is a related but distinct phenomenon
and it belongs in the realm of semantics,
because it is not affected by the context.

5. The president was assassinated entails The
president is dead. If the first utterance is true,
the second one is
automatically also true - one proposition logically
follows the other one.

6. There are three types of entailment:
Formal or logical entailment
Analytic entailment
Synthetic entailment