Question

what is gerund.?!...also describe its 1 rule with example

Answer 1

gerund is also a participle in which ing is used.
playing football is good for health. here playing is gerund. gerund is placed near the verv

Answer 2

Gerund is the verb which contains ing words or V4 form of the verb.
Rule - Gerunds are only used in the continuous tense.
Ex - She is playing, in this playing is the gerund.