Question

what is meant by affirmative

Answer 1

Affirmative means (in terms of English) Agrreing with a statement or request.

(In terms of Grammar) Affirmative means Positive.

Answer 2

Essentially an affirmative (positive) form is used to express the validity or truth of a basic assertion, while a negative form expresses its falsity.
Examples are the sentences "Jane is here" and "Jane is not here"; the first is affirmative, while the second is negative.