-며 means "and at the same time" and have two main usages.
1. used as meaning of "and, or"
이것은 책상이며 저것은 의자이다.
This is a table and that is a chair
그녀는 노래며 연주며 모두 잘하는 음악가이다.
She is a musician who are good at singing and playing.
2. used as meaning of "while, as, over, during, with" same to "-면서"
나는 신문을 보며(면서) 밥을 먹었다.
I read newspaper and ate food at the same time.
While reading newspaper, I ate food.
그것은 행복이며 기쁨이다.
It is happiness and also pleasure.