This is the 16222nd most frequent Russian word.
рассказывая
"Рассказывая" means "telling" or "narrating."
The word 'рассказывая' functions as a gerund, indicating the action of recounting happening during the evening.
Она провела вечер, рассказывая о своих приключениях.
She spent the evening recounting her adventures.
Here, 'рассказывая' describes the simultaneous action of narrating as he walked.
Он шел по улице, рассказывая веселую историю друзьям.
He was walking down the street, telling a funny story to his friends.
The word indicates the ongoing action of explaining or narrating about his project while engaged in another activity.